3. Discussion
inflammation, arterial vascular stiffness, CVD
CVD, INFLAMMATION, ARTERIAL STIFFNESS, OXIDATIVE STRESS, ENDOTHELIAL DYSFUNCTION
This paper shows one of the first studies of a head-to-head comparison in which all three devices, the filter cigarette, e-cigarette with nicotine-containing liquid, and heated tobacco product as well as the control arm of the e-cigarette with nicotine-free liquid, were examined within one study for inflammation, endothelial dysfunction, and arterial stiffness. In summary, we were able to show in our study not only an increase in the cellular immune response for all nicotine delivery devices and the combustible cigarette but also an increase in inflammatory markers and proinflammatory cytokines with a correlation to clinical data of arterial stiffness.For the filter cigarette, path mechanisms for the risk of developing CVD have been shown in various studies so far. The smoke from a combustible cigarette led to an increase in markers of oxidative stress [Notably, our results showed changes in white blood cell count with an increase in leukocytes as well as monocytes. These findings are also in line with the findings for the combustible cigarette where the transient increase in white blood cells is a well-established cardiovascular risk factor [Our results of the proinflammatory cytokines are also in line with the findings of Lee [The consumption of cigarettes and IQOS also leads to increased CO levels in the air we breathe. As described at the beginning, CO leads to an increase in vasoconstriction and thus also leads to endothelial dysfunction. However, a change in the endothelium is therefore not a separate process of CO or pro-inflammatory markers but is multifactorially conditioned.Another unique feature of this work is the link between the laboratory results and the measurements of arterial vascular stiffness. This means that the effects of proinflammatory cytokines and white blood cell count as well as endothelial dysfunction based on them explain the acute changes in PWV and the augmentation index for the different nicotine delivery devices as well as the combustible cigarette.Unfortunately, the investigative approach also has weaknesses. This includes, among other things, the very short observation period, so that only acute effects and no chronic effects can be observed, which should urgently be addressed in follow-up projects. In addition, the 20 test subjects constitute a rather small number of study participants. Due to the small number of subjects of each of the different experimental approaches, we have combined the two studies to consider the relationship between inflammation, arterial vascular stiffness, and endothelial dysfunction. Furthermore, we made supplementary laboratory tests and calculated additional statistics trying to add further explanations. A significant increase in the number of participants would lead to more valid measurement results. It is also not possible to verify with certainty whether all participants smoked or vapourised the respective devices exactly as specified. In addition, a correlation to the nicotine concentrations in the serum would be valuable in order to correlate the effects described in previous publications independently of the increasing serum-nicotine levels in this work.