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Black carbon (BC) aerosol is considered one of the most important contributors to rapid climate warming as well as snow and sea ice melting in the Arctic, yet the observations of BC aerosols in the Arctic Ocean have been limited due to infrastructural and logistical difficulties. We observed BC mass concentrations (mBC) using light absorption methods on board the icebreaker R/V Araon in the Arctic Ocean (< 80° N and 166° E to 156° W) as well as the North Pacific Ocean in summer and early autumn of 2016–2020. The levels, interannual variations, and pollution episodes of mBC in the Arctic were examined, and the emission sources responsible for the high-BC episodes were analyzed with global chemistry-transport-model simulations. The average mBC in the surface air over the Arctic Ocean (72–80° N) observed by the 2019 cruise exceeded 70 ng m -3 , which was substantially higher than that observed by cruises in other years (approximately 10 ng m -3). The much higher mBC observed in 2019 was perhaps due to more frequent wildfires occurring in the Arctic region than in other years. The model suggested that biomass burning contributed most to the observed BC by mass in the western Arctic Ocean and the marginal seas. For these 5 years, we identified 10 high-BC episodes north of 65° N, including one in 2018 that was associated with co-enhancements of CO and CH 4 but not CO 2 and O 3. The model analysis indicated that certain episodes were attributed to BC-containing air masses transported from boreal fire regions to the Arctic Ocean, with some transport occurring near the surface and others in the mid-troposphere. This study provides crucial datasets on BC mass concentrations and the mixing ratios of O 3 , CH 4 , CO, and CO 2 in the western Arctic Ocean regions, and it highlights the significant impact of boreal fires on the observed Arctic BC during the summer and early autumn months. [ABSTRACT FROM AUTHOR]

BackgroundAll mucosal epithelia, including those of the tubotympanium, are secreting a variety of antimicrobial innate immune molecules (AIIMs). In our previous study, we showed the bactericidal/bacteriostatic functions of AIIMs against various otitis media pathogens. Among the AIIMs, human beta-defensin 2 is the most potent molecule and is inducible by exposure to inflammatory stimuli such as bacterial components or proinflammatory cytokines. Even though the beta-defensin 2 is an important AIIM, the induction mechanism of this molecule has not been clearly established. We believe that this report is the first attempt to elucidate NTHi induced beta-defensin expression in airway mucosa, which includes the middle ear.MethodsMonoclonal antibody blocking method was employed in monitoring the TLR-dependent NTHi response. Two gene knock down methods - dominant negative (DN) plasmid and small interfering RNA (siRNA) - were employed to detect and confirm the involvement of several key genes in the signaling cascade resulting from the NTHi stimulated beta-defensin 2 expression in human middle ear epithelial cell (HMEEC-1). The student's t-test was used for the statistical analysis of the data.ResultsThe experimental results showed that the major NTHi-specific receptor in HMEEC-1 is the Toll-like receptor 2 (TLR2). Furthermore, recognition of NTHi component(s)/ligand(s) by TLR2, activated the Toll/IL-1 receptor (TIR)-MyD88-IRAK1-TRAF6-MKK3/6-p38 MAPK signal transduction pathway, ultimately leading to the induction of beta-defensin 2.ConclusionThis study found that the induction of beta-defensin 2 is highest in whole cell lysate (WCL) preparations of NTHi, suggesting that the ligand(s) responsible for this up-regulation may be soluble macromolecule(s). We also found that this induction takes place through the TLR2 dependent MyD88-IRAK1-TRAF6-p38 MAPK pathway, with the primary response occurring within the first hour of stimulation. In combination with our previous studies showing that IL-1alpha-induced beta-defensin 2 expression takes place through a MyD88-independent Raf-MEK1/2-ERK MAPK pathway, we found that both signaling cascades act synergistically to up-regulate beta-defensin 2 levels. We propose that this confers an essential evolutionary advantage to the cells in coping with infections and may serve to amplify the innate immune response through paracrine signaling.

BackgroundDespite its direct connection to the nasopharynx which harbors otitis media pathogens as part of its normal flora, the middle ear cavity is kept free of these bacteria by as yet unknown mechanisms. Respiratory mucosal epithelia, including those of the middle ear and eustachian tube, secrete antimicrobial effectors including lysozyme, lactoferrin and beta defensins-1 and -2. To elucidate the role of these innate immune molecules in the normal defense and maintenance of sterility of respiratory mucosa such as that of the middle ear, we assessed their effect on the respiratory pathogens nontypeable Haemophilus influenzae (NTHi) 12, Moraxella catarrhalis 035E, and Streptococcus pneumoniae 3, and 6B.MethodsTwo assay methods, the radial assay and the liquid broth assay, were employed for testing the antimicrobial activity of the molecules. This was done in order to minimize the possibility that the observed effects were artifacts of any single assay system employed. Also, transmission electron microscopy (TEM) was employed to evaluate the effect of antimicrobial innate immune molecules on OM pathogens. For the statistical analysis of the data, Student's t-test was performed.ResultsResults of the radial diffusion assay showed that beta defensin-2 was active against all four OM pathogens tested, while treatment with beta defensin-1 appeared to only affect M. catarrhalis. The radial assay results also showed that lysozyme was quite effective against S. pneumoniae 3 and 6B and was partially bacteriostatic/bactericidal against M. catarrhalis. Lysozyme however, appeared not to affect the growth of NTHi. Thus, lysozyme seems to have a more pronounced impact on the growth of the Gram-positive S. pneumoniae as compared to that of Gram-negative pathogens. Lactoferrin on the other hand, enhanced the growth of the bacteria tested. The results of the radial assays were confirmed using liquid broth assays for antimicrobial activity, and showed that lysozyme and beta defensin-2 could act synergistically against S. pneumoniae 6B. Moreover, in the liquid broth assay, beta defensin-1 showed a modest inhibitory effect on the growth of S. pneumoniae 6B. As assessed by ultrastructural analysis, lysozyme and beta defensin-2, and to a much lesser extent, beta defensin-1, appeared to be able to cause damage to the bacterial membranes.ConclusionsHere we report that lysozyme and the beta defensins can inhibit the growth of clinical isolates of otitis media pathogens - namely NTHi strain 12, S. pneumoniae strains 3 and 6B and M. catarrhalis strain 035E - and cause ultrastructural damage to these pathogens. Moreover, we demonstrate that lysozyme and beta defensin-2 can act synergistically against S. pneumoniae. These findings are consistent with the concept that secreted antimicrobial peptides and other components of innate immunity constitute the first line of defense protecting host mucosal surfaces, including the tubotympanal (eustachian tube and middle ear cavity) mucosa, against pathogens.

Black carbon (BC) aerosol is considered one of the important contributors to the fast climate warming and snow and sea ice melting in the Arctic. Yet the observations of BC in the Arctic Ocean have been limited due to infrastructural and logistical difficulties. We observed BC mass concentrations (m BC) using light absorption methods on board the icebreaker R/V Araon in the Arctic Ocean (166° E–156° W and <80° N) as well as the North Pacific Ocean in summer and early Autumn of 2016 to 2020. The levels, interannual variations and pollution episodes of m BC in the Arctic were examined, and the emission sources responsible for the high-BC episodes were analyzed with global chemistry-transport model simulations. The average m BC in the surface air over the Arctic Ocean (72–80° N) observed in 2019 was over 70 ng m–3, which was substantially higher than in other years (approximately 10 ng m–3). The much higher m BC observed in 2019 was perhaps due to more frequent wildfires occurred in the Arctic region than in other years. The model suggested that biomass burning composed the largest contribution to the observed BC in the western Arctic Ocean and the marginal seas. For these five years, we identified 10 elevated-BC episodes, including one in 2018 that was associated with co-enhancements of CO and CH4 but not CO2 and O3. The model analysis indicated that most episodes were attributed to the airmasses transported from boreal fires to the Arctic Ocean, with some near-surface and others in the mid-troposphere. This study provides crucial datasets on BC mass concentrations and the mixing ratios of O3, CH4, CO, and CO2 in the western Arctic Ocean regions and highlights the significant impact of boreal fires on the observed Arctic BC during the summer and early autumn months. [ABSTRACT FROM AUTHOR]