Trypanocidal and cysteine protease inhibitory activity of isopentyl caffeate is not linked in Trypanosoma brucei

Previously, it was reported that caffeic acid esters inhibit the growth of bloodstream forms of Trypanosoma brucei and the activity of its major lysosomal cathepsin l-like cysteine protease, TbCATL. However, whether this trypanocidal activity is due to inactivation of TbCATL has not so far been demonstrated. Caffeic acid isopentyl ester (isopentyl caffeate) displayed antitrypanosomal activity against T. brucei bloodstream forms with minimum inhibitory concentration (MIC) and 50 % growth inhibition (GI50) values of 1 and 0.31 μg/ml, respectively. The ester also inhibited the activity of purified TbCATL but with a 27-fold higher half maximal inhibitory concentration (IC50) value of 8.5 μg/ml compared to its GI50 value. In contrast to previous suggestion, isopentyl caffeate did not interact with the active site of TbCATL but inhibited the enzyme in a non-competitive way. In addition, the ester was ineffective in blocking the proteolysis in the lysosome of the parasite, which, however, is a hallmark for inhibitors whose trypanocidal action is through inactivation of TbCATL. These results suggest that the antitrypanosomal activity of isopentyl caffeate (and probably of other caffeic acid esters) cannot be attributed to inhibition of TbCATL. Nevertheless, caffeic acid esters are interesting compounds with promising antitrypanosomal activity. This is supported by a more than 100 times less sensitivity of human HL-60 cells to isopentyl caffeate indicating that the ester has a favourable selectivity profile

Bornyl caffeate induces apoptosis in human breast cancer MCF-7 cells via the ROS- and JNK-mediated pathways

AIM: The purpose of the present study was to investigate the anticancer activity of bornyl caffeate in the human breast cancer cell line MCF-7. METHODS: The cell viability was determined using the MTT assay, and apoptosis was initially defined by monitoring the morphology of the cell nuclei and staining an early apoptotic biomarker with Annexin V-FITC. The mitochondrial membrane potential was visualized by JC-1 under fluorescence microscopy, whereas intracellular reactive oxygen species (ROS) were assessed by flow cytometry. The expression of apoptosis-associated proteins was determined by Western blotting analysis. RESULTS: Bornyl caffeate induced apoptosis in MCF-7 cells in a dose- and time-dependent manner. Consistently, bornyl caffeate increased Bax and decreased Bcl-xl, resulting in the disruption of MMP and subsequent activation of caspase-3. Moreover, bornyl caffeate triggered the formation of ROS and the activation of the mitogen-activated protein (MAP) kinases p38 and c-Jun N-terminal kinase (JNK). Antioxidants attenuated the activation of MAP kinase p38 but barely affected the activation of JNK. Importantly, the cytotoxicity of bornyl caffeate was partially attenuated by scavenging ROS and inhibited by MAP kinases and caspases. CONCLUSION: The present study demonstrated that bornyl caffeate induced apoptosis in the cancer cell line MCF-7 via activating the ROS- and JNK-mediated pathways. Thus, bornyl caffeate may be a potential anticancer lead compound