Abstract
The 18 kDa translocator protein (TSPO) is mainly located in the outer mitochondrial membrane, widely spread throughout the body tissues and is abundant particularly in steroid-synthesizing organs. Cigarette smoke (CS) is considered as a major risk factor for the development of oral, lung, and cardiovascular diseases, as well as cancers. TSPO protein expression is elevated in cells exposed to CS, which subsequently results in increased TSPO-related cellular processes. CS-induced overexpression of TSPO may lead to interference with cellular functioning and eventually to tissue damage, and promotes the development of various pathologies, mainly oral, lung, and cardiovascular diseases. TSPO is involved in intra-cellular functions such as apoptosis, inflammation, proliferation, and regulation of mitochondrial membrane potential. Hence, the CS-induced upregulation of the TSPO expression may contribute to the development of malignant and non-malignant oral, lung and cardiovascular diseases, including tumor growth, progression, and metastasis. Therefore, TSPO may be a target for novel treatments for various CS-associated pathologies.
Keywords
Cigarette smoke (CS), Translocator protein (TSPO), Cardiovascular disease (CVD), Cancer
Background
Cigarette smoke (CS) is a main risk factor for the development of various diseases, either via direct exposure of tissues to CS [1-3] or indirect exposure of remote organs to CS extracts (CSE) (Figure 1) [4-6]. The harmful impact is induced by exposure to the toxic CS substances, each cigarette contains approximately 7,000 chemicals. Out of these chemicals, 250 compounds are considered harmful to tissues, and 69 of them can be involved in the emergence of cancer [7].
The 18 kDa translocator protein (TSPO) was previously named as the peripheral benzodiazepine receptor (PBR), as it was first localized in rat kidneys [8], and can be found in prokaryotes and eukaryotes [9,10]. To be distinguished from the central benzodiazepine receptors (CBR), it was referred as the PBR due its distribution in peripheral tissues outside the central nervous system (CNS), and its affinity to specific benzodiazepines (e.g. Ro5-4864). TSPO is expressed in various tissues across the body, with the highest expression in steroid- synthesizing endocrine organs [11,12], moderate expression in the kidneys and lungs [13-15], and with relatively low expression in the brain [16,17]. The TSPO name was attributed to this mitochondrial protein due to its ability to transport cholesterol across the outer mitochondrial membrane [12]. Inside the cell, TSPO is composed of five transmembrane helices across the outer mitochondrial membrane, which form a hydrophobic pocket that binds ligands at the cytosolic side of the mitochondria [18]. In the mitochondrial membrane, TSPO is found in association with the 32 kDa voltage-dependent anion channel (VDAC), and the 30-kDa adenine nucleotide translocator (ANT) [10,19]. TSPO plays an essential role in various intracellular functions including: apoptosis [10,20], cell proliferation [21-23], oxidative stress [24-26], and regulation of the mitochondrial membrane potential [26,27]. TSPO was found to be involved in the pathophysiology of traumatic brain injury [28,29], cancer [17,30,31], as well as in neuroinflammation and neurodegenerative diseases [17,32,33].
An interaction was found between CS and TSPO, showing an increase in TSPO protein expression levels starting after 60 mins of exposure of H1299 pulmonary epithelial cells to CS, but not after 30 mins [3]. It is likely that the main mechanism via which CS interferes with the physiological functioning is via induction of hypoxic conditions. In the lungs, the damage associated with CS is related primarily to inflammatory response, oxidative stress and proteolysis in the pulmonary epithelial lining, eventually leading to chronic obstructive pulmonary disease [34-36]. Another study demonstrated that CS-induced damage is related to elevation in the expression of the stress response protein regulated in development and DNA damage response-1 (REDD1). Such CS-induced upregulation of REDD1 expression is a result of the CS-related hypoxia [37]. Another main target for the devastating influence of CS is the cardiovascular system. The high content of free radicals and non-radical oxidants, such as superoxide generation may lead to lipid peroxidation and eventually to oxidative damage. This pathological impact of CS is linked with 3-fold higher risk of atherosclerotic damage to the cardiovascular system. This occurs mainly due to imbalance between the significantly increased oxidant levels and the downregulated protective antioxidants [36,38]. CS plays an essential role in the development of pulmonary diseases including chronic obstructive pulmonary disease (COPD) and cancer [2]. It was shown that a correlation exists between TSPO expression levels and the cancer aggressiveness, as upregulation of TSPO expression in cancer may modulate the activity of various cancer-related processes, such as cellular proliferation rate, angiogenesis, tumor cell migratory capability and adhesion [39]. This role of TSPO in cancer was demonstrated in different cancer types such as colorectal [25], breast [40], prostatic [41], ovarian [42] and colon [43,44] cancers.
The mechanism behind the damage caused by CS remains unclear and poorly understood [45,46]. It is possible that various mechanisms are involved in CS-related oral, pulmonary, and cardiovascular diseases [47-51]. Thus, the elucidation of the cellular and molecular mechanisms behind the occurrence of CS-related diseases is of great importance for the understanding of the pathophysiology of these diseases and the development of novel therapeutic agents.
Relevance of TSPO to Cancer
Alterations in TSPO binding and its expression levels are involved in the development of different pathological conditions. Currently, cancers are of major concern and TSPO expression was previously demonstrated to correlate with cancer aggressiveness [39].
One of the main cellular roles of TSPO is its antiapoptotic effect [10], which grants TSPO a protective role against cellular proliferation. Therefore, it seems that increased expression levels of TSPO aims to oppose the cancer’s excessive proliferation rate, growth, and spread of metastasis [39].
An interaction between CS, TSPO expression, and oral and lung cancers was demonstrated previously [3,52-56]. This interaction is reflected by the increased expression of TSPO in CS-induced oral and lung cancer models [3,53,55]. This interaction may indicate a possible role of TSPO as a novel target for the treatment of cancer [42-44,57], including oral and lung cancers.
Tumor aggressiveness is correlated with TSPO levels, and the cellular proliferation and survival rates of animals carrying cancerous cells can be attenuated by TSPO ligands [40,58-62]. Hardwick et al. investigated the involvement of over-expression of TSPO in cancerous tissues using southern blot and in situ fluorescence hybridization analysis. They reported elevated expression of the TSPO gene in aggressive metastatic tumor cells [60]. Thus, it seems that elevated TSPO gene expression in aggressive cancers may serve as an indicator of cancer progression. In addition, a positive correlation between TSPO expression and the metastatic potential of tumors was also demonstrated in human brain gliomas and astrocytomas [22,57], as well as in colorectal cancer [63].
Based on the accumulated data on the interaction between TSPO and cancer, Veenman et al. suggested that TSPO plays a role in cell proliferation and apoptosis, since TSPO ligands inhibit cell proliferation and increased survival rate in animal models of cancer [10].
CS, TSPO and CS-related Diseases
CS impact on [3H]PK11195 binding to TSPO
Our group assessed the impact of CS on the characteristics of [3H]PK11195 binding to TSPO in various tissues and cell lines. Some studies have shown that exposure to CS is associated with decreases in TSPO binding [6,53,56,64]. It appears that exposure to CS results in a decrease in TSPO binding. As described in Table 1. Exposure of lung cancer cells (H1299 cell line) is associated with a 2-fold decrease in the [3H]PK11195 binding following 60 mins of CS exposure [53]. Another study performed on saliva samples demonstrated a 30% decrease in [3H]PK11195 binding as compared to saliva not exposed to CS [56]. In addition, shorter exposure times to CS was shown to decrease the binding by 75% in cardiomyocytes exposed for 30 mins to CS [6]. Similar effects of CS on TSPO binding were also detected following longer CS exposure time (90 mins). In SCC-15 tongue cancer cells, a decrease in binding levels by 72% was detected at a concentration of 3 nM of [3H]PK11195, and by 56% at a concentration of 6 nM. In the case of SCC-25 tongue cancer cell line, a decrease in binding levels by 64% was seen at a concentration of 3 nM of [3H] PK11195 [52] (Table 1).
Cell type | CS exposure time (mins) |
Concentration of [3H]PK11195 (nM) |
Decrease in [3H]PK11195 binding | Reference |
---|---|---|---|---|
Tongue epithelium (SCC-15) |
90 | 3 | 64% | Nagler et al. [52] |
Tongue epithelium (SCC-25) |
90 | 3 | 72% | Nagler et al. [52] |
Lung epithelium | 60 | 6 | 2-fold | Nagler et al. [53] |
Saliva | 60 | 6 | 30% | Nagler et al. [56] |
Cardiomyocytes | 30 | 6 | 75% | Nagler et al. [6] |
Table 1: Decreases in [3H]PK 11195 binding to TSPO following exposure of different cell types to cigarette smoke for different durations.
It is possible that the deficient binding capacity of TSPO is involved in the development of CS-related diseases characterized by uncontrolled proliferation and growth of tissue leading to oral or lung cancer as well as to cardiovascular diseases. TSPO plays a role in cell death and apoptosis [10,65], thus, the CS-associated reduction in [3H]PK11195 binding to TSPO may lead to uncontrolled cell proliferation.
Cigarette smoke impact on TSPO protein expression
It was shown that exposure of cells to CS for prolonged time (30, 60, and 120 mins) resulted in increases in TSPO expression levels [3]. As mentioned before, in contrast to this finding, Nagler et al., reported a decrease in binding levels of the TSPO ligand [3H]PK11195 after 30 minutes of exposure of cardiomyocytes [6] as well as in saliva samples exposed for 60 minutes to CS [56]. It is possible that the upregulation of TSPO protein expression is a consequence of its decreased binding capability. In this manner, via the elevated TSPO protein expression, the cells attempt to provide a protective response to avoid cytotoxic damage. In contrast to the finding of elevated TSPO protein expression subsequent to CS exposure, Gavish et al. demonstrated a decrease in the expression of the tetrameric 72 kDa form of TSPO following 60 mins of CS exposure of H1299 lung cancer cells [66]. Thus, it appears that there is a complex relationship between CS, TSPO binding, and TSPO protein expression.
Cigarette Smoke, TSPO, Oral and Lung Cancers
CS is considered as a major risk factor for the development of oral cancer, along with other risk factors such as alcohol consumption, viral infections (mainly HPV-16 and 18), UV light and radiation [67,68]. CS is responsible for most oral cancer cases, and notably 75% of patients with oral cancer are smokers [69]. Tobacco expresses a type of synergism with alcohol, increasing further the risk for oral cancer development in alcohol users. Most oral cancers belong to the squamous cell carcinoma (SCC) family [69,70]. CS is involved also in the development of lung cancer due to the inhaled carcinogens into the alveolar spaces and the direct impact of these carcinogens on lung tissue [47]. Chronic smoking causes accumulating damages and alterations in the pulmonary tissue, and some of these damages are irreversible. The continuous irritation of the pulmonary epithelial lining might result in the appearance of pulmonary diseases such as COPD and other inflammation-related diseases, and eventually may also end in the development of lung cancer that is usually associated with high mortality rates [71,72].
The cancer-related increase in TSPO protein expression in lung cancer cell line (H1299) seems to be upregulated further following CS exposure [3]. This triad interaction (CS, TSPO, and cancer) in both the oral cavity and lung indicates the role of TSPO in CS-induced cancer in these tissues. Usually, oral and lung cancers are present in a more aggressive form in smokers, as compared to nonsmokers [69,73].
This complex association may indicate that TSPO-related pathways play a role in the development and progression of oral and lung cancer induced by CS.
Cigarette Smoke, TSPO, and Cardiovascular Diseases (CVDs)
The CS associated with exposure to various oxidizing agents from the combusted cigarettes, resulting in oxidation of various molecules in various tissues throughout the body [74,75].
In the cardiac tissue, the antioxidant system prevents oxidative damage to the myocardium by opposing the production of reactive oxygen species (ROS) [76]. Several studies reported on the impact of CS on TSPO and the TSPO-related mitochondrial processes, which eventually induce oxidative stress, and may cause cell death [3,6]. This association between CS exposure and the degree of the cellular damage was shown to correlate with increased ROS production, oxidative stress, and cell death in parallel to the CS exposure time. This interaction may be involved in the increased risk of CVD, cancers, and inflammatory diseases in chronic smokers [48,76-80].
The incidence of death in myocardial infarction (MI) patients mostly occurs due to coronary heart disease (CHD), with MI proposing a risk factor for heart failure and cardiac arrhythmias [78,79]. A linear correlation described by Whincup and colleagues, demonstrated the increased risk of CHD incidence in relation to increased amount of CS exposure (number of cigarettes smoked daily) [81]. Similarly, another study showed increased relative risk of CHD incidence in association with increased duration of CS exposure in patients under 70 years of age [82]. In contrast to these linear correlations, Law and Wald described a non-linear correlation between the risk for CHD incidence and the increased amount of CS exposure. The authors suggested that the absence of the linear correlation is due to the low threshold of the effect of smoking on the risk to develop a CHD, thus display a more steady incremental fashion [49]
Penna et al. suggested that the mitochondrial permeability transition pore opening may be altered by the ischemiareperfusion injury to cardiomyocytes, which leads to apoptosis and necrosis to commence and eventually results in MI [50]. Sensitivity to ischemia was shown to be modulated by TSPO ligands, acting as attenuators of ROS generation, which can be further modulated by activation or blockade of the inner membrane anion channel (IMAC) in the mitochondria. Such alterations attenuate the mitochondrial depolarization levels and the duration of the action potential, imposing an antiarrhythmic impact. In this respect, several studies suggested that activation of IMAC resulted in increased sensitivity to ischemia of cardiomyocytes [76,83]. Briefly, the application of TSPO ligands was shown to possess a cardioprotective effect, via reducing ROS generation and thus decreasing the risk for arrhythmia and MI [84,85]
Conclusions
Various studies described the putative role of TSPO and the downstream TSPO-related processes in CS-induced cytotoxic damages in association to disease development. Further comprehensive studies are warranted to clarify the underlying mechanisms in the involvement of TSPO in disease and cancer development. In addition, thorough in vivo investigation of the efficacy of TSPO ligands to prevent or attenuate CS-induced cytotoxicity is needed in appropriate animal models. The accumulated data may promote the development of innovative treatments of CSinduced diseases using TSPO ligands in TSPO-intact and in TSPO-knockdown cells, tissues, and transgenic mice, as well as in human clinical trials.
References
2. Vainio H, Wilbourn JD, Sasco AJ, Partensky C, Gaudin N, Heseltine E, et al. Identification of human carcinogenic risks in IARC monographs. Bulletin du cancer. 1995;82(5):339-48.
3. Zeineh N, Nagler R, Gabay M, Weizman A, Gavish M. Effects of cigarette smoke on tspo-related mitochondrial processes. Cells. 2019 Jul;8(7):694.
4. Fricker M, Goggins BJ, Mateer S, Jones B, Kim RY, Gellatly SL, et al. Chronic cigarette smoke exposure induces systemic hypoxia that drives intestinal dysfunction. JCI Insight. 2018 Feb 8;3(3).
5. Kamceva G, Arsova-Sarafinovska Z, Ruskovska T, Zdravkovska M, Kamceva-Panova L, Stikova E. Cigarette smoking and oxidative stress in patients with coronary artery disease. Open access Macedonian Journal of Medical Sciences. 2016 Dec 15;4(4):636-40.
6. Nagler R, Zeineh N, Azrad M, Yassin N, Weizman A, Gavish M. 18-kDa Translocator Protein Ligands Protect H9C2 Cardiomyocytes from Cigarette Smoke-induced Cell Death: In Vitro Study. In Vivo. 2020 Mar 1;34(2):549-56.
7. Berridge MS, Apana SM, Nagano KK, Berridge CE, Leisure GP, Boswell MV. Smoking produces rapid rise of [11 C] nicotine in human brain. Psychopharmacology. 2010 May 1;209(4):383-94.
8. Braestrup C, Squires RF. Specific benzodiazepine receptors in rat brain characterized by high-affinity (3H) diazepam binding. Proceedings of the National Academy of Sciences. 1977 Sep 1;74(9):3805-9.
9. Bonsack F, Sukumari-Ramesh S. TSPO: an evolutionarily conserved protein with elusive functions. International journal of molecular sciences. 2018 Jun;19(6):1694.
10. Veenman L, Papadopoulos V, Gavish M. Channellike functions of the 18-kDa translocator protein (TSPO): regulation of apoptosis and steroidogenesis as part of the host-defense response. Current Pharmaceutical Design. 2007 Aug 1;13(23):2385-405.
11. Souza EB, Anholt RR, Murphy KM, Snyder SH, Kuhar MJ. Peripheral-type benzodiazepine receptors in endocrine organs: autoradiographic localization in rat pituitary, adrenal, and testis. Endocrinology. 1985 Feb 1;116(2):567-73.
12. Papadopoulos V, Baraldi M, Guilarte TR, Knudsen TB, Lacapère JJ, Lindemann P, et al. Translocator protein (18 kDa): new nomenclature for the peripheraltype benzodiazepine receptor based on its structure and molecular function. Trends in Pharmacological Sciences. 2006 Aug 1;27(8):402-9.
13. Anholt RR, De Souza EB, Oster-Granite ML, Snyder SH. Peripheral-type benzodiazepine receptors: autoradiographic localization in whole-body sections of neonatal rats. Journal of Pharmacology and Experimental Therapeutics. 1985 May 1;233(2):517-26.
14. Morohaku K, Phuong NS, Selvaraj V. Developmental expression of translocator protein/peripheral benzodiazepine receptor in reproductive tissues. PloS One. 2013 Sep 5;8(9):e74509.
15. Wang HJ, Fan J, Papadopoulos V. Translocator protein (Tspo) gene promoter-driven green fluorescent protein synthesis in transgenic mice: an in vivo model to study Tspo transcription. Cell and Tissue Research. 2012 Nov 1;350(2):261-75.
16. Chen MK, Guilarte TR. Translocator protein 18 kDa (TSPO): molecular sensor of brain injury and repair. Pharmacology & therapeutics. 2008 Apr 1;118(1):1-7.
17. Rupprecht R, Papadopoulos V, Rammes G, Baghai TC, Fan J, Akula N, et al. Translocator protein (18 kDa) (TSPO) as a therapeutic target for neurological and psychiatric disorders. Nature Reviews Drug discovery. 2010 Dec;9(12):971.
18. Jaremko Ł, Jaremko M, Giller K, Becker S, Zweckstetter M. Structure of the mitochondrial translocator protein in complex with a diagnostic ligand. Science. 2014 Mar 21;343(6177):1363-6
19. McEnery MW, Snowman AM, Trifiletti RR, Snyder SH. Isolation of the mitochondrial benzodiazepine receptor: association with the voltage-dependent anion channel and the adenine nucleotide carrier. Proceedings of the National Academy of Sciences. 1992 Apr 15;89(8):3170-4.
20. Veenman L, Gavish M. The role of 18 kDa mitochondrial translocator protein (TSPO) in programmed cell death, and effects of steroids on TSPO expression. Current Molecular Medicine. 2012 May 1;12(4):398-412.
21. Beinlich A, Strohmeier R, Kaufmann M, Kuhl H. Relation of cell proliferation to expression of peripheral benzodiazepine receptors in human breast cancer cell lines. Biochemical Pharmacology. 2000 Aug 1;60(3):397- 402.
22. Miettinen H, Kononen J, Haapasalo H, Helén P, Sallinen P, Harjuntausta T, et al. Expression of peripheraltype benzodiazepine receptor and diazepam binding inhibitor in human astrocytomas: relationship to cell proliferation. Cancer Research. 1995 Jun 15;55(12):2691- 5.
23. Papadopoulos V. In search of the function of the peripheral-type benzodiazepine receptor. Endocrine Research. 2004 Jan 1;30(4):677-84.
24. Veenman L, Shandalov Y, Gavish M. VDAC activation by the 18 kDa translocator protein (TSPO), implications for apoptosis. Journal of Bioenergetics and Biomembranes. 2008 Jun 1;40(3):199-205.
25. Shoukrun R, Veenman L, Shandalov Y, Leschiner S, Spanier I, Karry R, et al. The 18-kDa translocator protein, formerly known as the peripheral-type benzodiazepine receptor, confers proapoptotic and antineoplastic effects in a human colorectal cancer cell line. Pharmacogenetics and Genomics. 2008 Nov 1;18(11):977-88.
26. Kugler W, Veenman L, Shandalov Y, Leschiner S, Spanier I, Lakomek M, et al. Ligands of the mitochondrial 18 kDa translocator protein attenuate apoptosis of human glioblastoma cells exposed to erucylphosphohomocholine. Analytical Cellular Pathology. 2008 Jan 1;30(5):435-50.
27. Veenman L, Alten J, Linnemannstöns K, Shandalov Y, Zeno S, Lakomek M, et al. Potential involvement of F 0 F 1-ATP (synth) ase and reactive oxygen species in apoptosis induction by the antineoplastic agent erucylphosphohomocholine in glioblastoma cell lines. Apoptosis. 2010 Jul 1;15(7):753-68.
28. Gavish M, Bachman I, Shoukrun R, Katz Y, Veenman L, Weisinger G, et al. Enigma of the peripheral benzodiazepine receptor. Pharmacological Reviews. 1999 Dec 1;51(4):629-50.
29. Toulmond S, Duval D, Serrano A, Scatton B, Benavides J. Biochemical and histological alterations induced by fluid percussion brain injury in the rat. Brain Research. 1993 Aug 20;620(1):24-31.
30. Bai M, Rone MB, Papadopoulos V, Bornhop DJ. A novel functional translocator protein ligand for cancer imaging. Bioconjugate Chemistry. 2007 Nov 21;18(6):2018-23.
31. Vlodavsky E, Soustiel JF. Immunohistochemical expression of peripheral benzodiazepine receptors in human astrocytomas and its correlation with grade of malignancy, proliferation, apoptosis and survival. Journal of Neuro-oncology. 2007 Jan 1;81(1):1-7.
32. Chauveau F, Boutin H, Van Camp N, Dollé F, Tavitian B. Nuclear imaging of neuroinflammation: a comprehensive review of [11 C] PK11195 challengers. European Journal of Nuclear Medicine and Molecular Imaging. 2008 Dec 1;35(12):2304-19.
33. Liu GJ, Middleton RJ, Hatty CR, Kam WW, Chan R, Pham T, et al. The 18 kDa translocator protein, microglia and neuroinflammation. Brain Pathology. 2014 Nov;24(6):631-53.
34. Daijo H, Hoshino Y, Kai S, Suzuki K, Nishi K, Matsuo Y, et al. Cigarette smoke reversibly activates hypoxiainducible factor 1 in a reactive oxygen species-dependent manner. Scientific Reports. 2016 Sep 29;6:34424.
35. Demedts IK, Demoor T, Bracke KR, Joos GF, Brusselle GG. Role of apoptosis in the pathogenesis of COPD and pulmonary emphysema. Respiratory Research. 2006 Dec;7(1):1-0.
36. Tagawa Y, Hiramatsu N, Kasai A, Hayakawa K, Okamura M, Yao J, et al. Induction of apoptosis by cigarette smoke via ROS-dependent endoplasmic reticulum stress and CCAAT/enhancer-binding protein-homologous protein (CHOP). Free Radical Biology and Medicine. 2008 Jul 1;45(1):50-9.
37. Yoshida T, Mett I, Bhunia AK, Bowman J, Perez M, Zhang L, et al. Rtp801, a suppressor of mTOR signaling, is an essential mediator of cigarette smoke–induced pulmonary injury and emphysema. Nature Medicine. 2010 Jul;16(7):767-73.
38. Marangon K, Herbeth B, Lecomte E, Paul-Dauphin A, Grolier P, Chancerelle Y, et al. Diet, antioxidant status, and smoking habits in French men. The American Journal of Clinical Nutrition. 1998 Feb 1;67(2):231-9.
39. Bode J, Veenman L, Caballero B, Lakomek M, Kugler W, Gavish M. The 18 kDa translocator protein influences angiogenesis, as well as aggressiveness, adhesion, migration, and proliferation of glioblastoma cells. Pharmacogenetics and Genomics. 2012 Jul 1;22(7):538- 50.
40. Papadopoulos V, Kapsis A, Li H, Amri H, Hardwick M, Culty M, et al. Drug-induced inhibition of the peripheral-type benzodiazepine receptor expression and cell proliferation in human breast cancer cells. Anticancer Research. 2000;20(5A):2835-47.
41. Fafalios A, Akhavan A, Parwani AV, Bies RR, McHugh KJ, Pflug BR. Translocator protein blockade reduces prostate tumor growth. Clinical Cancer Research. 2009 Oct 1;15(19):6177-84.
42. Katz Y, Ben-Baruch G, Kloog Y, Menczer J, Gavish M. Increased density of peripheral benzodiazepine-binding sites in ovarian carcinomas as compared with benign ovarian tumours and normal ovaries. Clinical Science. 1990 Feb;78(2):155-8.
43. Katz Y, Eitan A, Amiri Z, Gavish M. Dramatic increase in peripheral benzodiazepine binding sites in human colonic adenocarcinoma as compared to normal colon. European Journal of Pharmacology. 1988;148(3):483-4.
44. Katz Y, Eitan A, Gavish M. Increase in peripheral benzodiazepine binding sites in colonic adenocarcinoma. Oncology. 1990;47(2):139-42.
45. Jha P, Peto R. Global effects of smoking, of quitting, and of taxing tobacco. New England Journal of Medicine. 2014 Jan 2;370(1):60-8.
46. Kung HC, Hoyert DL, Xu J, Murphy SL. Deaths: final data for 2005. National Vital Statistics Reports. 2008 Apr 24;56(10):1-20.
47. Bhalla DK, Hirata F, Rishi AK, Gairola CG. Cigarette smoke, inflammation, and lung injury: a mechanistic perspective. Journal of Toxicology and Environmental Health, Part B. 2009 Jan 8;12(1):45-64.
48. Hasnis E, Reznick AZ, Pollack S, Klein Y, Nagler RM. Synergistic effect of cigarette smoke and saliva on lymphocytes—the mediatory role of volatile aldehydes and redox active iron and the possible implications for oral cancer. The International Journal of Biochemistry & Cell Biology. 2004 May 1;36(5):826-39.
49. Law MR, Wald NJ. Environmental tobacco smoke and ischemic heart disease. Progress in Cardiovascular Diseases. 2003 Jul 1;46(1):31-8.
50. Penna C, Perrelli MG, Pagliaro P. Mitochondrial pathways, permeability transition pore, and redox signaling in cardioprotection: therapeutic implications. Antioxidants & Redox Signaling. 2013 Feb 10;18(5):556- 99.
51. Skillrud DM, Offord KP, Miller RD. Higher risk of lung cancer in chronic obstructive pulmonary disease: a prospective, matched, controlled study. Annals of Internal Medicine. 1986 Oct 1;105(4):503-7.
52. Nagler R, Ben-Izhak O, Savulescu D, Krayzler E, Akrish S, Leschiner S, et al. Oral cancer, cigarette smoke and mitochondrial 18 kDa translocator protein (TSPO)—In vitro, in vivo, salivary analysis. Biochimica et Biophysica Acta (BBA)-Molecular Basis of Disease. 2010 May 1;1802(5):454-61.
53. Nagler R, Cohen S, Gavish M. The effect of cigarette smoke on the translocator protein (TSPO) in cultured lung cancer cells. Journal of Cellular Biochemistry. 2015 Dec;116(12):2786-92.
54. Zeno S, Zaaroor M, Leschiner S, Veenman L, Gavish M. CoCl2 induces apoptosis via the 18 kDa translocator protein in U118MG human glioblastoma cells. Biochemistry. 2009 Jun 2;48(21):4652-61.
55. Nagler R, Savulescu D, Krayzler E, Leschiner S, Veenman L, Gavish M. Cigarette smoke decreases salivary 18 kDa translocator protein binding affinity-in association with oxidative stress. Current Medicinal Chemistry. 2010 Aug 1;17(23):2539-46.
56. Nagler R, Savulescu D, Gavish M. Cigarette smokeinduced reduction in binding of the salivary translocator protein is not mediated by free radicals. Biochimie. 2016 Feb 1;121:1-4.
57. Batarseh A, Li J, Papadopoulos V. Protein kinase Cε regulation of translocator protein (18 kDa) Tspo gene expression is mediated through a MAPK pathway targeting STAT3 and c-Jun transcription factors. Biochemistry. 2010 Jun 15;49(23):4766-78.
58. Galiègue S, Casellas P, Kramar A, Tinel N, Simony- Lafontaine J. Immunohistochemical assessment of the peripheral benzodiazepine receptor in breast cancer and its relationship with survival. Clinical cancer research. 2004 Mar 15;10(6):2058-64.
59. Han Z, Slack RS, Li W, Papadopoulos V. Expression of peripheral benzodiazepine receptor (PBR) in human tumors: relationship to breast, colorectal, and prostate tumor progression. Journal of Receptors and Signal Transduction. 2003 Jan 1;23(2-3):225-38.
60. Hardwick M, Cavalli LR, Barlow KD, Haddad BR, Papadopoulos V. Peripheral-type benzodiazepine receptor (PBR) gene amplification in MDA-MB-231 aggressive breast cancer cells. Cancer Genetics and Cytogenetics. 2002 Nov 1;139(1):48-51.
61. Hardwick M, Rone J, Han Z, Haddad B, Papadopoulos V. Peripheral-type benzodiazepine receptor levels correlate with the ability of human breast cancer MDA-MB-231 cell line to grow in scid mice. International Journal of Cancer. 2001 Nov 1;94(3):322-7.
62. Hardwick M, Fertikh D, Culty M, Li H, Vidic B, Papadopoulos V. Peripheral-type benzodiazepine receptor (PBR) in human breast cancer: correlation of breast cancer cell aggressive phenotype with PBR expression, nuclear localization, and PBR-mediated cell proliferation and nuclear transport of cholesterol. Cancer Research. 1999 Feb 15;59(4):831-42.
63. Maaser K, Höpfner M, Jansen A, Weisinger G, Gavish M, Kozikowski AP, et al. Specific ligands of the peripheral benzodiazepine receptor induce apoptosis and cell cycle arrest in human colorectal cancer cells. British Journal of Cancer. 2001 Dec;85(11):1771-80.
64. Gavish A, Krayzler E, Nagler R. Two populations of TSPO binding sites in oral cancer SCC-15 cells. Experimental Cell Research. 2017 Jan 1;350(1):279-83.
65. Levin E, Premkumar A, Veenman L, Kugler W, Leschiner S, Spanier I, et al. The peripheral-type benzodiazepine receptor and tumorigenicity: isoquinoline binding protein (IBP) antisense knockdown in the C6 glioma cell line. Biochemistry. 2005 Jul 26;44(29):9924- 35.
66. Gavish M, Cohen S, Nagler R. Cigarette smoke effects on TSPO and VDAC expression in a cellular lung cancer model. European Journal of Cancer Prevention. 2016 Sep 1;25(5):361-7.
67. Neville BW. Update on current trends in oral and maxillofacial pathology. Head and Neck Pathology. 2007 Sep 1;1(1):75-80.
68. Graham S, Dayal H, Rohrer T, Swanson M, Sultz H, Shedd D, et al. Dentition, diet, tobacco, and alcohol in the epidemiology of oral cancer. Journal of the National Cancer Institute. 1977 Dec 1;59(6):1611-8.
69. Graham S, Dayal H, Rohrer T, Swanson M, Sultz H, Shedd D, et al. Dentition, diet, tobacco, and alcohol in the epidemiology of oral cancer. Journal of the National Cancer Institute. 1977 Dec 1;59(6):1611-8.
70. Mello FW, Melo G, Pasetto JJ, Silva CA, Warnakulasuriya S, Rivero ER. The synergistic effect of tobacco and alcohol consumption on oral squamous cell carcinoma: a systematic review and meta-analysis. Clinical Oral Investigations. 2019 Jul 1:1-1.
71. Woodard GA, Jones KD, Jablons DM. Lung cancer staging and prognosis. InLung Cancer 2016 (pp. 47-75). Springer, Cham.
72. Thorley AJ, Tetley TD. Pulmonary epithelium, cigarette smoke, and chronic obstructive pulmonary disease. International journal of chronic obstructive pulmonary disease. 2007 Dec;2(4):409.
73. Rivera GA, Wakelee H. Lung Cancer in Never Smokers. Advances in Experimental Medicine and Biology. 2016 Jan 01;893:43-57.
74. Burke A, FitzGerald GA. Oxidative stress and smokinginduced vascular injury. Progress in Cardiovascular Diseases. 2003 Jul 1;46(1):79-90.
75. Nowak JA, Murray JJ, Oates JA, FitzGerald GA. Biochemical evidence of a chronic abnormality in platelet and vascular function in healthy individuals who smoke cigarettes. Circulation. 1987 Jul;76(1):6-14.
76. Motloch LJ, Hu J, Akar FG. The mitochondrial translocator protein and arrhythmogenesis in ischemic heart disease. Oxidative medicine and cellular longevity. 2015 Mar 30;2015.
77. Krayzler E, Nagler RM. Carbonyl levels and survival rates in oral cancer cells exposed to cigarette smoke. Anticancer Research. 2015 Apr 1;35(4):1961-5.
78. Lerner DJ, Kannel WB. Patterns of coronary heart disease morbidity and mortality in the sexes: a 26-year follow-up of the Framingham population. American Heart Journal. 1986 Feb 1;111(2):383-90.
79. Writing Group Members, Lloyd-Jones D, Adams RJ, Brown TM, Carnethon M, Dai S, et al. Executive summary: heart disease and stroke statistics—2010 update: a report from the American Heart Association. Circulation. 2010 Feb 23;121(7):948-54.
80. Zorov DB, Juhaszova M, Sollott SJ. Mitochondrial ROS-induced ROS release: an update and review. Biochimica et Biophysica Acta (BBA)-Bioenergetics. 2006 May 1;1757(5-6):509-17.
81. Whincup PH, Gilg JA, Emberson JR, Jarvis MJ, Feyerabend C, Bryant A, et al. Passive smoking and risk of coronary heart disease and stroke: prospective study with cotinine measurement. BMJ. 2004 Jul 22;329(7459):200- 5.
82. In How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General. 2010: Atlanta (GA).
83. Akar FG, Aon MA, Tomaselli GF, O’Rourke B. The mitochondrial origin of postischemic arrhythmias. The Journal of Clinical Investigation. 2005 Dec 1;115(12):3527- 35.
84. Obame FN, Zini R, Souktani R, Berdeaux A, Morin D. Peripheral benzodiazepine receptor-induced myocardial protection is mediated by inhibition of mitochondrial membrane permeabilization. Journal of Pharmacology and Experimental Therapeutics. 2007 Oct 1;323(1):336- 45.
85. Xiao J, Liang D, Zhang H, Liu Y, Li F, Chen YH. 4′-Chlorodiazepam, a translocator protein (18 kDa) antagonist, improves cardiac functional recovery during postischemia reperfusion in rats. Experimental Biology and Medicine. 2010 Apr;235(4):478-86.