Machine Learning and Meteorological Normalization for Assessment of Particulate Matter Changes during the COVID-19 Lockdown in Zagreb, Croatia.

In this paper, the authors investigated changes in mass concentrations of particulate matter (PM) during the Coronavirus Disease of 2019 (COVID-19) lockdown. Daily samples of PM1, PM2.5 and PM10 fractions were measured at an urban background sampling site in Zagreb, Croatia from 2009 to late 2020. For the purpose of meteorological normalization, the mass concentrations were fed alongside meteorological and temporal data to Random Forest (RF) and LightGBM (LGB) models tuned by Bayesian optimization. The models' predictions were subsequently de-weathered by meteorological normalization using repeated random resampling of all predictive variables except the trend variable. Three pollution periods in 2020 were examined in detail: January and February, as pre-lockdown, the month of April as the lockdown period, as well as June and July as the "new normal". An evaluation using normalized mass concentrations of particulate matter and Analysis of variance (ANOVA) was conducted. The results showed that no significant differences were observed for PM1, PM2.5 and PM10 in April 2020-compared to the same period in 2018 and 2019. No significant changes were observed for the "new normal" as well. The results thus indicate that a reduction in mobility during COVID-19 lockdown in Zagreb, Croatia, did not significantly affect particulate matter concentration in the long-term..

Pollution levels and deposition processes of airborne organic pollutants over the central Adriatic area: Temporal variabilities and source identification.

First data on polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) in aerosols as well as of PAHs, polychlorinated biphenyls (PCBs) and NACs in bulk and wet atmospheric deposition samples were simultaneously obtained during 6-month-long field campaign at the costal central Adriatic area. Special attention was given to open-fire biomass burning episodes as extreme events common for the overall Mediterranean coastal area in order to gain a better understanding of the atmospheric variabilities and potential sources of trace organic pollutants in coastal environments. Diesel and gasoline combustion related to land and maritime traffic as well as occasional open-fire episodes (forest fires) were found to be the dominant pollution sources of PAHs in PM10 particles. NACs were determined almost exclusively in samples affected by biomass burning episodes. Open-fire episodes had a strong contribution to the overall NACs atmospheric deposition fluxes. Several chlorinated congeners of PCBs were predominantly contributed in deposition samples.

An optimized sample preparation and analysis method for the determination of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in the atmospheric bulk deposition samples.

A method based on solid phase extraction (SPE), gas chromatography tandem mass spectrometry (GC-MS/MS) and gas chromatography with electron capture detector (GC-ECD) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in atmospheric deposition samples. Six indicator PCB congeners were analysed by GC-ECD equipped with two micro electron-capture detectors and two gas chromatographic columns, while 12 PAH compounds were analysed by GC-MS/MS. Solid phase extraction on silica sorbent proved suitable for accumulation of PAHs and PCBs from deposited matters. The extraction procedure was based by passing the whole sample volume through a silica cartridge with dichloromethane and n-hexane as the eluting solvents. Two different performances of a bulk collector were compared. The method was validated using field total deposited samples collected monthly over a year by bulk method at an urban background station in Zagreb, Croatia. The levels and occurrence of PCBs corresponded to global environmental pollution, with the deposition rates of ∑6PCBs between 6 - 28 ng m-2 d-1. The deposition rates of ∑12PAHs varied between 132 and 714 ng m-2 d-1 during the warm period, whereas it achieved a significantly higher range of 171 to 1069 ng m-2 d-1 in the cold period.

Isotherm, kinetic, and thermodynamic study of ciprofloxacin sorption on sediments.

In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The K d parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin-Radushkevich (D-R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated K d values varied from 171 to 37,347 mL/g. The obtained values of E (free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained n values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (R 2 > 0.999). Thermodynamic parameters including the Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.

A preliminary evaluation of leukocyte phospho-glucocorticoid receptor as a potential biomarker of depressogenic vulnerability in healthy adults.

The mechanism of maladaptive chronic stress response involves altered phosphorylation of the glucocorticoid receptor (GR). In this study, we investigated if important depressogenic vulnerability factors, such as neuroticism and self-reports of negative affective states, may be associated with alterations in levels of the GR and GR phosphoisoforms in peripheral blood mononuclear cells (PBMC) of healthy adults. In 21 women and 16 men we evaluated PMBC levels of total GR (tGR), GR phosphorylated at serine 211 (pGR-S211) and serine 226 (pGR-S226) and correlated these data with personality traits and current reports of stress, anxiety and depression. Also, we assessed plasma cortisol levels in all tested subjects. Our results showed that in women nuclear pGR-S226 was positively correlated with neuroticism and current reports of depression, anxiety and stress, while the ratio of nuclear pGR-S211/pGR-S226 was negatively correlated with reports of depression. None of the aforementioned correlations were significant in men. No significant relations between cortisol levels and any of GR parameters were observed. These preliminary findings highlight the value of GR phosphorylation-related research in identifying molecular biomarkers of depressogenic vulnerability, at least in women.

Gender-specific effects of fluoxetine on hippocampal glucocorticoid receptor phosphorylation and behavior in chronically stressed rats.

Chronic psychosocial isolation stress (CPSI) modulates glucocorticoid receptor (GR) functioning in Wistar male rat hippocampus (HIPPO) through alteration of nuclear GR phosphorylation and its upstream kinases signaling, which parallels animal depressive-like behavior. The current study investigated potential gender specificities regarding the effect of chronic therapy by an antidepressant fluoxetine (FLU) on GR signaling in HIPPO and depressive-like behavior in CPSI animals. FLU was administrated to female and male naïve or CPSI rats for 21 days and GR protein, its phosphorylation status and upstream kinases, as well as GR and BDNF mRNA were followed in HIPPO together with animal serum corticosterone (CORT) and depressive-like behavior. The results showed that CPSI increased immobility in males versus hyperactivity in females and disrupted nuclear pGR232-Cdk5 pathway and JNK signaling in a gender-specific way. In contrast, in both genders CPSI increased the nuclear levels of GR and pGR246 but decreased CORT and mRNA levels of GR and BDNF. Concomitant FLU normalized the depressive-like behavior and altered the nuclear pGR232-Cdk5 signaling in a gender-specific manner. In both females and males, FLU reversed the nuclear levels of GR and pGR246 without affecting CORT and GR mRNA levels. In contrast, FLU exhibited gender-specific effect on BDNF mRNA in CPSI animals, by increasing it in females, but not in males. In spite of normalization the total nuclear GR level upon FLU treatment in both gender, down-regulation of GR mRNA is possibly maintained through prevalence of pGR232 isoform only in males. The gender-specific alterations of pGR232-Cdk5 signaling and BDNF gene expression in HIPPO and normalization of depressive-like behavior upon FLU treatment distinguishes this signaling pathway as potential future antidepressant target for gender-specific therapy of stress related mood disorders.

Phosphorylation of leukocyte glucocorticoid receptor in patients with current episode of major depressive disorder.

The impaired glucocorticoid receptor (GR) signaling has long been considered one of the cornerstones in understanding the pathophysiology of depression. Since the phosphorylation of GR is very important for GR function, in this study we investigated whether GR phosphorylation at serine 211 (pGR-S211) and serine 226 (pGR-S226) is altered in patients with current episode of major depressive disorder (MDD). Particularly, in 30 MDD patients and 35 controls we assessed the levels of nuclear total GR (tGR), pGR-S211 and pGR-S226 in peripheral blood mononuclear cells (PBMC) using Western blot technique, along with plasma cortisol concentrations from the same blood samples. Our results demonstrated increased phosphorylation of GR at S226 (p<0.001) and, to a less extent, at S211 (p<0.05) in MDD patients compared to controls. Consequently, the pGR-S211/pGR-S226 ratio was decreased (p<0.05) implying reduced transcriptional activity of GR in MDD patients. MDD subjects had higher cortisol levels than controls and cortisol concentrations were positively correlated with PBMC pGR-S226 levels from the same blood samples. There was no difference in the levels of tGR between MDD and control subjects. The study showed that altered phosphorylation of GR could contribute to impaired GR function related to the pathophysiology of depression.

Chronic stress decreases availability of heat shock proteins to glucocorticoid receptor in response to novel acute stress in Wistar rat hypothalamus.

Chronic psychosocial isolation (CPSI) is known to cause several maladaptive changes in the limbic brain structures, which regulate the hypothalamic-pituitary-adrenal (HPA) axis activity. In this study, we focused our investigation on CPSI effects in the hypothalamus (HT) since it is a major driver of HPA axis activity. We also investigated whether the exposure to CPSI could alter the response to subsequent acute stress (30-min immobilization). In the HT, we followed cytosolic and nuclear levels of the glucocorticoid receptor (GR), as a mediator of HPA axis feedback inhibition, and its chaperones, the heat shock proteins (HSPs), hsp70 and hsp90. The CPSI did not cause any changes in either GR or HSPs levels. However, we observed increase of the GR and hsp70 in both HT cellular compartments as a response of naïve rats to acute stress, whereas the response of CPSI rats to acute stress was associated with elevation of the GR in the cytosol and decrease of HSPs in the nucleus. Thus, our data indicated reduced availability of HSPs to GR in both cytosol and nucleus of the HT under acute stress of CPSI animals, and therefore, pointed out to potentially negative effects of CPSI on GR function in the HT.

Fluoxetine decreases glutathione reductase in erythrocytes of chronically isolated wistar rats.

Alterations in the antioxidative defense parameters upon chronic stress are considered critical for pathophysiology of stress related psychiatric disorders, and their status in blood serves as biomarker for effects of pharmacological treatments. The present study was designed to investigate the modulation of erythrocyte antioxidant enzymes (AOEs): CuZn superoxide dismutase (CuZnSOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GLR) activities and their protein expression in Wistar male rats subjected to chronic psychosocial isolation and/or to pharmacological treatment with fluoxetine. Chronically isolated animals exhibited decreased levels of serum corticosterone, as opposed to other chronic stress paradigms. In addition to that, SOD, CAT and GPx status was not altered either by chronic psychosocial isolation or by fluoxetine treatment. In contrast, GLR activity and its protein level were both markedly reduced by fluoxetine. Since, GLR is crucial for overall oxido-reductive balance through maintaining optimal ratio of reduced/oxidized glutathione level (GSH/GSSG) in erythrocytes, these results could indicate that in spite of numerous beneficial effects of fluoxetine, it may compromise both haemoglobin function and oxygen transport.