Aleksandar Backovic

Cigarette smoke – an aging accelerator?

Cigarette smoking reduces life span by an average of 7 years, and tobacco consumption accounts for a shortening of disease free life by 14 years. The exact mechanisms by which smoking causes disease and death are generally not well understood, but evidence continues to mount that cigarette smoking exhausts cellular defense and repair functions, leading to an accumulation of damage e.g. mutations and malfunctioning proteins. In this review, we make an attempt to ascribe many of the deleterious effects of smoking on human health to a general principle, namely the acceleration of aging processes by cigarette smoke chemicals.

The immunology of fibrosis: innate and adaptive responses

Fibrosis is an important health problem, and its pathogenetic principles are still largely unknown. It can develop either spontaneously, or, more frequently, as a consequence of various underlying diseases. Irrespective of the primary cause, however, fibrotic tissue is always infiltrated by mononuclear immune cells. In most instances the reason for the attraction of these cells to fibrotic tissue and their proliferation remains to be determined; however their cytokine profile shows clear-cut proinflammatory and profibrotic characteristics. In this review, we discuss the innate and adaptive immune reactions associated with the development of fibrosis and the molecular basis of the profibrotic mechanisms taking place in systemic sclerosis (scleroderma), arteriosclerosis and peri-silicone mammary implant fibrosis.

Cigarette smoke extract induces prolonged endoplasmic reticulum stress and autophagic cell death in human umbilical vein endothelial cells

AIMS Consumption of cigarette smoke (CS) is a well-known risk factor for early atherosclerosis; yet, the underlying mechanisms of smoking-associated atherosclerosis are poorly understood. Based on the previous results indicating that CS-induced endothelial cell death neither shows typical features of apoptosis nor of necrosis, we investigated the role of autophagy in CS extract (CSE)-induced cell death of human umbilical vein endothelial cells (HUVECs). METHODS AND RESULTS Here, we demonstrate that overexpression of the classical apoptosis inhibitor BCL-XL had no protective effect on CSE-induced cell death, whereas the autophagy inhibitor 3-methyladenin and an shRNAi-mediated knockdown of the autophagy mediator ATG5 significantly delayed cell death. Our results indicate that CSE induces an excess accumulation of misfolded proteins in the endoplasmic reticulum (ER) and consequently the onset of the unfolded protein response. We provide evidence that the ER-resident kinase PERK is a major transducer of ER stress leading to phosphorylation of eIF2α and attenuation of protein synthesis. Finally, we show that prolonged ER stress in cells subjected to CS is followed by activation of an autophagic programme. CSE-induced autophagy is characterized by an increase in LC3 II/I ratio and activation ATG12. The autophagic signalling pathway via energy depletion and consequent activation AMP-activated protein kinase could be excluded. CONCLUSION Our results confirm and extend previous findings reporting on the induction of autophagy by CSE in the lung. We show that protein damage caused by CSE activates autophagy, ultimately resulting in necrotic death of HUVECs. Via this mechanism, cigarette smoking may contribute to the deterioration of vascular endothelial function and the initiation of atherosclerosis.

Cigarette smoke is an endothelial stressor and leads to cell cycle arrest

The molecular mechanisms underlying the atherogenic activity of cigarette smoke have yet to be fully elucidated. In the present study, genome-wide microarray analysis was performed on endothelial cells exposed to an aqueous cigarette smoke extract (CSE) for 3, 7, and 24 h, to obtain a better insight into how smoking may lead to endothelial damage. Microarray analysis showed the transcriptional response to CSE was dominated by heat shock, stress responsive, and inflammatory genes, along with genes encoding for anti-oxidant and metal detoxification proteins. The heat shock response was shown to be a result of short lived reactive species of CSE, with the abrogation of the effect by the addition of old CSE, the anti-oxidant N-acetyl cysteine, or the removal of metals from CSE implying that reactive oxygen species are the main culprit. This was further supported by a strong decline in the level of intracellular protein oxidation levels seen under these conditions compared to freshly prepared CSE. Mitochondrial integrity was also found to be significantly compromised after CSE treatment, resulting in a threefold increase in depolarised mitochondria after 6 h. Finally, cell cycle analysis showed the induction of G1 cell cycle arrest. An increased stress and inflammation response indicates that endothelial damage from smoking could contribute to immune cell infiltration, while decreased growth rates reduce endothelial layer repair, promoting atherogenesis.