Products of 5-lipoxygenase and myeloperoxidase activities are increased in young male cigarette smokers

Molecular and functional changes in neutrophilic granulocytes induced by nicotine: a systematic review and critical evaluation

Background

Over 1.1 billion people smoke worldwide. The alkaloid nicotine is a prominent and addictive component of tobacco. In addition to tumors and cardiovascular disorders, tobacco consumption is associated with a variety of chronic-inflammatory diseases. Although neutrophilic granulocytes (neutrophils) play a role in the pathogenesis of many of these diseases, the impact of nicotine on neutrophils has not been systematically reviewed so far.

Objectives

The aim of this systematic review was to evaluate the direct influence of nicotine on human neutrophil functions, specifically on cell death/damage, apoptosis, chemotaxis, general motility, adhesion molecule expression, eicosanoid synthesis, cytokine/chemokine expression, formation of neutrophil extracellular traps (NETs), phagocytosis, generation of reactive oxygen species (ROS), net antimicrobial activity, and enzyme release.

Material and methods

This review was conducted according to the PRISMA guidelines. A literature search was performed in the databases NCBI Pubmed® and Web of Science™ in February 2023. Inclusion criteria comprised English written research articles, showing in vitro studies on the direct impact of nicotine on specified human neutrophil functions.

Results

Of the 532 originally identified articles, data from 34 articles were finally compiled after several evaluation steps. The considered studies highly varied in methodological aspects. While at high concentrations (>3 mmol/l) nicotine started to be cytotoxic to neutrophils, concentrations typically achieved in blood of smokers (in the nmol/l range) applied for long exposure times (24-72h) supported the survival of neutrophils. Smoking-relevant nicotine concentrations also increased the chemotaxis of neutrophils towards several chemoattractants, elevated their production of elastase, lipocalin-2, CXCL8, leukotriene B4 and prostaglandin E2, and reduced their integrin expression. Moreover, while nicotine impaired the neutrophil phagocytotic and anti-microbial activity, a range of studies demonstrated increased NET formation. However, conflicting effects were found on ROS generation, selectin expression and release of β-glucuronidase and myeloperoxidase.

Conclusion

Nicotine seems to support the presence in the tissue and the inflammatory and selected tissue-damaging activity of neutrophils and reduces their antimicrobial functions, suggesting a direct contribution of nicotine to the pathogenesis of chronic-inflammatory diseases via influencing the neutrophil biology.

Early and Sustained Increases in Leukotriene B4 Levels Are Associated with Poor Clinical Outcome in Ischemic Stroke Patients

Leukotriene B4 (LTB4) has been implicated in ischemic stroke pathology. We examined the prognostic significance of LTB4 levels in patients with acute middle cerebral artery (MCA) infarction and their mechanisms in rat stroke models. In ischemic stroke patients with middle cerebral artery infarction, plasma LTB4 levels were found to increase rapidly, roughly doubling within 24 h when compared to initial post-stroke levels. Further analyses indicate that poor functional recovery is associated with early and more sustained increase in LTB4 rather than the peak levels. Results from studies using a rat embolic stroke model showed increased 5-lipoxygenase (5-LOX) expression in the ipsilateral infarcted cortex compared with sham control or respective contralateral regions at 24 h post-stroke with a concomitant increase in LTB4 levels. In addition, neutrophil influx was also observed in the infarcted cortex. Double immunostaining indicated that neutrophils express 5-LOX and leukotriene A4 hydrolase (LTA4H), highlighting the pivotal contributions of neutrophils as a source of LTB4. Importantly, rise in plasma LTB4 levels corresponded with an increase in LTB4 amount in the infarcted cortex, thereby supporting the use of plasma as a surrogate for brain LTB4 levels. Pre-stroke LTB4 loading increased brain infarct volume in tMCAO rats. Conversely, administration of the 5-LOX-activating protein (FLAP) inhibitor BAY-X1005 or B-leukotriene receptor (BLTR) antagonist LY255283 decreased the infarct volume by a similar extent. To conclude, targeted interruption of the LTB4 pathway might be a viable treatment strategy for acute ischemic stroke.

Laser Photobiomodulation in the acute inflammatory response of the calcaneal tendon injury in rats exposed to cigarette smoke

ABSTRACT Nicotine delays the healing process and increases the levels of myeloperoxidase (MPO), an enzyme that plays a key role in the production of reactive oxygen species during the inflammatory process. Laser Photobiomodulation (PBM) is one of the most used electrophysical agents in the treatment of the calcaneal tendon, however, its effects on MPO activity need to be further elucidated. This study aimed to evaluate the effects of laser PBM on MPO activity after inflicting an injury to the calcaneal tendon of rats exposed to cigarette smoke. Thirty-four male Wistar rats with 90 days of age were used. After 14 days of exposure to cigarette smoke, the animals were divided into three experimental groups: control group (CG, n=12), not submitted to injury or treatment; sham group (ShG, n=10), submitted to partial calcaneal tendon injury and laser PBM simulation; and laser PBM group (PBMG, n=12), submitted to partial calcaneal tendon lesion and treated with laser PBM within the first minute after injury. PBM decreased MPO activity levels in PBMG compared to ShG (CG: 1.38±0.69pg/ml; ShG: 3.78±1.09pg/ml; PBMG: 2.58±0.93pg/ml; p<0.005). In conclusion, applying laser PBM immediately after inflicting damage to the calcaneal tendon attenuates acute inflammatory activity in rats exposed to cigarette smoke.

Immune Dysregulation in Cancer Patients Undergoing Immune Checkpoint Inhibitor Treatment and Potential Predictive Strategies for Future Clinical Practice

Realization of the full potential of immune checkpoint inhibitor-targeted onco-immunotherapy is largely dependent on overcoming the obstacles presented by the resistance of some cancers, as well as on reducing the high frequency of immune-related adverse events (IRAEs) associated with this type of immunotherapy. With the exception of combining therapeutic monoclonal antibodies, which target different types of immune checkpoint inhibitory molecules, progress in respect of improving therapeutic efficacy has been somewhat limited to date. Likewise, the identification of strategies to predict and monitor the development of IRAEs has also met with limited success due, at least in part, to lack of insight into mechanisms of immunopathogenesis. Accordingly, considerable effort is currently being devoted to the identification and evaluation of strategies which address both of these concerns and it is these issues which represent the major focus of the current review, particularly those which may be predictive of development of IRAEs. Following an introductory section, this review briefly covers those immune checkpoint inhibitors currently approved for clinical application, as well as more recently identified immune checkpoint inhibitory molecules, which may serve as future therapeutic targets. The remaining and more extensive sections represent overviews of: (i) putative strategies which may improve the therapeutic efficacy of immune checkpoint inhibitors; (ii) recent insights into the immunopathogenesis of IRAEs, most prominently enterocolitis; and (iii) strategies, mostly unexplored, which may be predictive of development of IRAEs.

Dietary Plant Sterols Supplementation Increases In Vivo Nitrite and Nitrate Production in Healthy Adults: A Randomized, Controlled Study

A randomized, double-blinded, placebo-controlled and crossover study was conducted to simultaneously measure the effects, 3 h after consumption and after 4-wk daily exposure to plant sterols-enriched food product, on in vivo nitrite and nitrate production in healthy adults. Eighteen healthy participants (67% female, 35.3 [mean] ± 9.5 [SD] years, mean body mass index 22.8 kg/m² ) received 2 soy milk (20 g) treatments daily: placebo and one containing 2.0 g free plant sterols equivalent of their palmityl esters (β-sitosterol, 55%; campesterol, 29%; and stigmasterol, 23%). Nitrite and nitrate concentrations were measured in the blood plasma and urine, using stable isotope-labeled gas chromatography-mass spectrometry. L-arginine and asymmetric dimethylarginine concentrations in blood serum were measured using commercially available enzyme immunoassays. Nitrite and nitrate concentrations in blood plasma (nitrite 5.83 ± 0.50 vs. 4.52 ± 0.27; nitrate 15.78 ± 0.96 vs. 13.43 ± 0.81 μmol/L) and urine (nitrite 1.12 ± 0.22 vs. 0.92 ± 0.36, nitrate 12.23 ± 1.15 vs. 9.71 ± 2.04 μmol/L) were significantly elevated after 4-wk plant sterols supplementation Placebo and 3-h treatments did not affect the blood plasma and urinary concentrations of nitrite and nitrate. Circulating levels of L-arginine and asymmetric dimethylarginine were unchanged in the placebo and treatment arms. Total plant sterols, β-Sitosterol, campesterol, and stigmasterol concentrations were significantly elevated after 4-wk treatments compared to the placebo and 3-h treatments. Blood plasma nitrite and nitrate concentrations correlated significantly with the plasma total and specific plant sterol concentrations. Our results suggest that dietary plant sterols, in the combination used, can upregulate nitrite, and nitrate production in vivo.

Role of myeloperoxidase in abdominal aortic aneurysm formation: mitigation by taurine

Oxidative stress plays a fundamental role in abdominal aortic aneurysm (AAA) formation. Activated polymorphonuclear leukocytes (or neutrophils) are associated with AAA and express myeloperoxidase (MPO), which promotes inflammation, matrix degradation, and other pathological features of AAA, including enhanced oxidative stress through generation of reactive oxygen species. Both plasma and aortic MPO levels are elevated in patients with AAA, but the role of MPO in AAA pathogenesis has, heretofore, never been investigated. Here, we show that MPO gene deletion attenuates AAA formation in two animal models: ANG II infusion in apolipoprotein E-deficient mice and elastase perfusion in C57BL/6 mice. Oral administration of taurine [1% or 4% (wt/vol) in drinking water], an amino acid known to react rapidly with MPO-generated oxidants like hypochlorous acid, also prevented AAA formation in the ANG II and elastase models as well as the CaCl2 application model of AAA formation while reducing aortic peroxidase activity and aortic protein-bound dityrosine levels, an oxidative cross link formed by MPO. Both MPO gene deletion and taurine supplementation blunted aortic macrophage accumulation, elastin fragmentation, and matrix metalloproteinase activation, key features of AAA pathogenesis. Moreover, MPO gene deletion and taurine administration significantly attenuated the induction of serum amyloid A, which promotes ANG II-induced AAAs. These data implicate MPO in AAA pathogenesis and suggest that studies exploring whether taurine can serve as a potential therapeutic for the prevention or treatment of AAA in patients merit consideration.NEW & NOTEWORTHY Neutrophils are abundant in abdominal aortic aneurysm (AAA), and myeloperoxidase (MPO), prominently expressed in neutrophils, is associated with AAA in humans. This study demonstrates that MPO gene deletion or supplementation with the natural product taurine, which can scavenge MPO-generated oxidants, can prevent AAA formation, suggesting an attractive potential therapeutic strategy for AAA.

Relationship between rs854560 PON1 Gene Polymorphism and Tobacco Smoking with Coronary Artery Disease

Paraoxonase-1 (PON1) is the antioxidant marker of high-density lipoproteins protecting against atherosclerosis and coronary artery disease (CAD) phenotype. The purpose of the present study was to determine whether the PON1 gene rs854560 polymorphism (163T>A) is associated with CAD in Polish population. rs854560 was genotyped in 494 subjects: 248 patients with premature CAD and 246 blood donors as a control. We found that the risk of CAD was significantly higher in TT homozygotes than in A allele carriers (OR = 1.87, p = 0.041). The synergistic effect between the TT genotype and cigarette smoking was observed (SIM = 9.81; SI = 14.70). The relative increase in risk from interaction between factors was over 37 (RERI = 36.13). The PON1 polymorphism did not modulate the risk of CAD in response to exposure to other traditional risk factors. In conclusion, the rs854560 polymorphism may modulate the risk of CAD in response to cigarette smoking in Polish population. Carriers of TT genotype seem to be particularly at risk of CAD, when exposed to cigarette smoking.

Plant sterol-enriched soy milk consumption modulates 5-lipoxygenase, 12-lipoxygenase, and myeloperoxidase activities in healthy adults - a randomized-controlled trial

A randomized, double blind, placebo-controlled and crossover study was conducted to simultaneously measure the effects, after 3-h and 4-week daily exposure to plant sterols-enriched food product, on inflammation, oxidative status, 5-lipoxygenase, 12-lipoxygenase, and myeloperoxidase activities in healthy adults. Eighteen healthy participants (67% female, 35.3 (mean) ± 9.5 (SD) years, mean body mass index 22.8 kg m^-2) received two soy milk (20g) treatments daily: placebo and one containing 2.0 g free plant sterols equivalent of their palmitates (β-sitosterol, 55%; campesterol, 29%; stigmasterol, 23%). F₂-isoprostanes, leukotriene B₄, sitosterol, campesterol, and stigmasterol concentrations were measured in the blood plasma and urine, using stable isotope-labeled gas chromatography-mass spectrometry. High-sensitivity c-reactive protein, tumor necrosis factor-_α, and lipoxin A₄ concentrations in blood serum were measured using commercially available enzyme immunoassays. Myeloperoxidase activity, serum lipid hydroperoxides, plasma and urinary F₂-isoprostanes, plasma and urinary leukotriene B₄, and plasma high-sensitivity c-reactive protein concentrations were significantly reduced, while circulating lipoxin A₄ concentrations were significantly elevated after 4-week plant sterols treatment. Plant sterols treatment decreased plasma leukotriene B₄ and increased plasma lipoxin A₄ concentrations acutely. Total plant sterols, β-sitosterol, campesterol, and stigmasterol concentrations were significantly elevated after 4-week treatments compared with the pre-treatment concentrations. Our results suggest that dietary plant sterols, in the combination used, can alleviate lipid peroxidation and inflammatory events in vivo. These effects are possibly exerted via the modulation of myeloperoxidase, 5-lipoxygenase, and 12-lipoxygenase activities.

Improvement in blood pressure after short-term inorganic nitrate supplementation is attenuated in cigarette smokers compared to non-smoking controls

Dietary supplementation with inorganic nitrate (NO₃^-) has been reported to improve cardiovascular health indices in healthy adults. Cigarette smoking increases circulating thiocyanate (SCN^-), which has been suggested to competitively inhibit salivary nitrate (NO₃^-) uptake, a rate-limiting step in dietary NO₃^- metabolism. Therefore, this study tested the hypothesis that dietary NO₃^- supplementation would be less effective at increasing the circulating plasma nitrite concentration ([NO₂^-]) and lowering blood pressure in smokers (S) compared to non-smokers (NS). Nine healthy smokers and eight healthy non-smoking controls reported to the laboratory at baseline (CON) and following six day supplementation periods with 140 mL day^-1 NO₃^--rich (8.4 mmol NO₃^- day^-1; NIT) and NO₃^--depleted (0.08 mmol NO₃^- day^-1; PLA) beetroot juice in a cross-over experiment. Plasma and salivary [SCN^-] were elevated in smokers compared to non-smokers in all experimental conditions (P < 0.05). Plasma and salivary [NO₃^-] and [NO₂^-] were elevated in the NIT condition compared to CON and PLA conditions in smokers and non-smokers (P < 0.05). However, the change in salivary [NO₃^-] (S: 3.5 ± 2.1 vs. NS: 7.5 ± 4.4 mM), plasma [NO₃^-] (S: 484 ± 198 vs. NS: 802 ± 199 μM) and plasma [NO₂^-] (S: 218 ± 128 vs. NS: 559 ± 419 nM) between the CON and NIT conditions was lower in the smokers compared to the non-smokers (P < 0.05). Salivary [NO₂^-] increased above CON to a similar extent with NIT in smokers and non-smokers (P > 0.05). Systolic blood pressure was lowered compared to PLA with NIT in non-smokers (P < 0.05), but not smokers (P > 0.05). These findings suggest that dietary NO₃^- metabolism is compromised in smokers leading to an attenuated blood pressure reduction compared to non-smokers after NO₃^- supplementation. These observations may provide novel insights into the cardiovascular risks associated with cigarette smoking and suggest that this population may be less likely to benefit from improved cardiovascular health if they increase dietary NO₃^- intake.

Analysis of Chlorination, Nitration, and Nitrosylation of Tyrosine and Oxidation of Methionine and Cysteine in Hemoglobin from Type 2 Diabetes Mellitus Patients by Nanoflow Liquid Chromatography Tandem Mass Spectrometry

The post-translational modification (PTM) of proteins by endogenous reactive chlorine, nitrogen, and oxygen species is implicated in certain pathological conditions, including diabetes mellitus. Evidence showed that the extents of modifications on a number of proteins are elevated in diabetic patients. Measuring modification on hemoglobin has been used to monitor the extent of exposure. This study develops an assay for simultaneous quantification of the extent of chlorination, nitration, and oxidation in human hemoglobin and to examine whether the level of any of these modifications is higher in poorly controlled type 2 diabetic mellitus patients. This mass spectrometry-based assay used the bottom-up proteomic strategy. Due to the low amount of endogenous modification, we first characterized the sites of chlorination at tyrosine in hypochlorous acid-treated hemoglobin by an accurate mass spectrometer. The extents of chlorination, nitration, and oxidation of a total of 12 sites and types of modifications in hemoglobin were measured by nanoflow liquid chromatography-nanospray ionization tandem mass spectrometry under the selected reaction monitoring mode. Relative quantification of these PTMs in hemoglobin extracted from blood samples shows that the extents of chlorination at α-Tyr-24, nitration at α-Tyr-42, and oxidation at the three methionine residues are significantly higher in diabetic patients (n = 19) than in nondiabetic individuals (n = 18). After excluding the factor of smoking, chlorination at α-Tyr-24, nitration at α-Tyr-42, and oxidation at the three methionine residues are significantly higher in the nonsmoking diabetic patients (n = 12) than in normal nonsmoking subjects (n = 11). Multiple regression analysis performed on the combined effect of age, body-mass index (BMI), and HbA1c showed that the diabetes factor HbA1c contributes significantly to the extent of chlorination at α-Tyr-24 in nonsmokers. In addition, age contributes to oxidation at α-Met-32 significantly in all subjects and in nonsmokers. These results suggest the potential of using chlorination at α-Tyr-24-containing peptide to evaluate protein damage in nonsmoking type 2 diabetes mellitus.

Relative Inhibitions of 5-Lipoxygenase and Myeloperoxidase and Free-Radical Scavenging Activities of Daidzein, Dihydrodaidzein, and Equol

The effects of bioavailability and metabolic transformation on the biological activities of daidzein are relatively unknown. The effects of daidzein, dihydrodaidzein, and equol at physiologically relevant concentrations on the production of leukotriene B4 and F2-isoprostanes, and myeloperoxidase enzyme activity in freshly isolated human neutrophils were examined. Equol, at physiological concentrations, inhibited leukotriene B4 production (IC50-200 nmol/L) in human neutrophils significantly more than daidzein and dihydrodaidzein (IC50 values >1000 nmol/L). Daidzein, dihydrodaidzein, and equol did not affect the enzymatic hydrolysis of leukotriene A4 to leukotriene B4, suggesting that they exerted their inhibitory effects on the 5-lipoxygenase activity. Daidzein (IC50 = 600 nmol/L) protected against free radical peroxidation of arachidonic acid significantly more than did equol and dihydrodaidzein (IC50 values >1000 nmol/L). Equol also showed significantly greater inhibition of myeloperoxidase activity (IC50 = 450 nmol/L) when compared to daidzein and dihydrodaidzein. Equol accumulated within the human neutrophils at significantly higher concentrations than daidzein and dihydrodaidzein after incubation with the three compounds at physiologically relevant concentrations. Neutrophils were able to accumulate intracellular daidzein, dihydrodaidzein, and equol up to a concentration of ∼600 nmol/L. Our results provide in vitro evidence that the biological activities of daidzein are profoundly influenced by bioavailability and metabolic transformation.

Interactions between paraoxonase 1 genetic polymorphisms and smoking and their effects on oxidative stress and lung cancer risk in a Korean population

Background

Few studies in epidemiology have evaluated the effects of gene-environment interaction on oxidative stress, even though this interaction is an important etiologic factor in lung carcinogenesis. We investigated the effects of the genetic polymorphisms of paraoxonase 1 (PON1), smoking, and the interaction between the two on lung cancer risk and oxidative stress.

Methods

This study’s subjects consisted of 416 newly diagnosed lung cancer patients and an equal number of matched controls. The GoldenGate assay was used for genotypic analyses of the PON1 gene. Urinary 8-hydroxydeoxyguanosine (8-OHdG) and thiobarbituric acid reactive substances levels were measured as indicators of oxidative stress.

Results

The PON1 rs662 AA genotype showed a significantly lower risk of lung cancer than the GG genotype (OR = 0.60, 95% CI: 0.36–0.99). The protective effect of the PON1 rs662 AA genotype on lung cancer risk was limited to non-smokers. Lung cancer patients who had the rs662 A allele showed a dose-dependent association between smoking status and oxidative stress markers. Among non-smoking lung cancer patients, urinary 8-OHdG levels were significantly lower in individuals with the rs662 GA and AA genotypes than in those with the GG genotype. Furthermore, we found a significant interaction effect between PON1 rs662 and smoking status on urinary 8-OHdG levels in lung cancer patients.

Conclusions

Our results suggest that the protective effect of PON1 rs662 SNP against lung carcinogenesis and the induction of oxidative stress might be modulated by the interaction between PON1 genetic polymorphisms and tobacco smoking.

Augmentation of 5-lipoxygenase activity and expression during dengue serotype-2 infection

BACKGROUND

Leukotriene B4, a 5-lipoxygenase product of arachidonic acid with potent chemotactic effects on neutrophils, has not been assessed in dengue patients. In this study, plasma leukotriene B4 and serum high-sensitivity C-reactive protein levels were determined in adult patients during the febrile, convalescent and defervescent stages of dengue serotype-2 (DENV-2) infection, and compared with those of age-matched healthy and non-dengue febrile subjects. In vitro studies were performed to examine the effects of live and heat-inactivated DENV-2 on the activities and expression of 5-lipoxygenase in human neutrophils.

RESULTS

Plasma leukotriene B4 was elevated during the febrile stages of dengue infection compared to levels during convalescence and in study controls. Plasma leukotriene B4 also correlated with serum high-sensitivity C-reactive protein in dengue patients (febrile, r = 0.91, p < 0.001; defervescence, r = 0.87, p < 0.001; convalescence, r = 0.87, p < 0.001). Exposure of human neutrophils to DENV-2 resulted in a significant rise in leukotriene B4; the extent of increase, however, did not differ between exposure to live and heat-inactivated DENV-2. Pre-incubation of either live or heat-inactivated DENV-2 resulted in reduced leukotriene B4 release by neutrophils, indicating that contact with dengue antigens (and not replication) triggers the neutrophil response. Production of leukotriene B4 was associated with an increase in 5-lipoxygenase expression in human neutrophils; addition of MK886 (a 5-lipoxygenase activating protein inhibitor) attenuated further increase in leukotriene B4 production.

CONCLUSION

These findings provide important clinical and mechanistic data on the involvement of 5-lipoxygenase and its metabolites in dengue infection. Further studies are needed to elucidate the therapeutic implications of these findings.

Cigarette smoking and mechanisms of susceptibility to infections of the respiratory tract and other organ systems

The predisposition of cigarette smokers for development of oral and respiratory infections caused by microbial pathogens is well recognised, with those infected with the human immunodeficiency virus (HIV) at particularly high risk. Smoking cigarettes has a suppressive effect on the protective functions of airway epithelium, alveolar macrophages, dendritic cells, natural killer (NK) cells and adaptive immune mechanisms, in the setting of chronic systemic activation of neutrophils. Cigarette smoke also has a direct effect on microbial pathogens to promote the likelihood of infective disease, specifically promotion of microbial virulence and antibiotic resistance. In addition to interactions between smoking and HIV infection, a number of specific infections/clinical syndromes have been associated epidemiologically with cigarette smoking, including those of the upper and lower respiratory tract, gastrointestinal tract, central nervous and other organ systems. Smoking cessation benefits patients in many ways, including reduction of the risk of infectious disease.