Background
Information about the harmful effects of vaping is sparse and inconsistent, therefore, since the use of electronic cigarettes (e-CIGs) has become increasingly popular as a tool to limit tobacco smoking, it is urgent to establish the safety or the toxicity of the liquid vaporized by the atomizer of the commercial e-CIGs.
Methods
Skin (HaCaT) and lung (A549) cells, the main targets of cigarette smoke, were exposed to e-CIG vapor (e-CIG Mini Touch T-Fumo T-TEX) and cigarette smoke (UK research cigarette) in a smoke chamber in vitro. The cytotoxic effect of the exposure was analyzed in both cell types by ultrastructural morphology, Trypan Blue exclusion test and LDH assay. In addition, pro-inflammatory cytokines were measured in culture medium by the Bio-Plex cytokine assay kit.
Results
The cytotoxic components of e-CIG were restrained to the flavoring compound and, to a lesser extent, to nicotine and their effects were comparable to that of cigarette smoke. Humectants alone exhibited no cytotoxicity but induced the release of cytokines and pro-inflammatory mediators, mainly in keratinocytes.
Conclusions
Based on our results, we can state that e-CIG vapors exposure is not completely harmless, although far less toxic than CS. In fact, besides the deleterious effect of flavor and nicotine, even the humectants alone are able to evocate some adverse cellular events, such as enhanced cytokines release. This study will hopefully promote the development of truly innocuous e-CIGs to help people quit smoking.
Because cancers are caused by deregulation of hundreds of genes, an ideal anticancer agent should target multiple gene products or signaling pathways simultaneously. Recently, extensive research has addressed the chemotherapeutic potential of plant-derived compounds. Among the ever-increasing list of naturally occurring anticancer agents, Rottlerin appears to have great potentiality for being used in chemotherapy because it affects several cell machineries involved in survival, apoptosis, autophagy, and invasion. The underlying mechanisms that have been described are diverse, and the final, cell-specific, Rottlerin outcome appears to result from a combination of signaling pathways at multiple levels. This paper seeks to summarize the multifocal signal modulatory properties of Rottlerin, which merit to be further exploited for successful prevention and treatment of cancer.
Rottlerin is a natural product isolated from Mallotus philippinensis. This polyphenolic compound, originally described as a selective inhibitor of PKCδ, can inhibit many other PKC-unrelated kinases and has a number of biological actions, including mitochondrial uncoupling effects. We recently found that Rottlerin inhibits the transcription factor nuclear factor κB in different cell types, causing downregulation of cyclin D1 and growth arrest. The present study was carried out to clarify the surprising lack of effect of Rottlerin on MCF-7 cell viability, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test. We found that Rottlerin causes overestimation of the MTT test, leading to inconsistent results between cell number and cell viability. Rottlerin, however, strongly differs from other antioxidant polyphenols, which directly reduce tetrazolium salts, since it does not exhibit any reactivity toward the tetrazolium salts in vitro nor does it modulate lactate dehydrogenase activity. The interference in the MTT assay occurred only in cultured cells, concomitantly with a decrease in the energy charge. Because the same MTT overestimation was observed in the presence of uncoupling agents, we conclude that the Rottlerin artifact is linked to its uncoupling action that, by accelerating oxidative chain, accidentally results in enhanced MTT reduction. These results suggest caution in the use of the MTT assay in the presence of Rottlerin and uncouplers in general.
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