DiGeorge syndrome critical region gene 8 (DGCR8) is the RNA-binding partner protein of the nuclease Drosha. DGCR8 and Drosha recognize and cleave primary transcripts of microRNAs (pri-miRNAs) in the maturation of canonical microRNAs (miRNAs) in animals. We previously reported that human, frog, and starfish DGCR8 bind heme when expressed in Escherichia coli and that Fe(III) heme activates apoDGCR8 in reconstituted pri-miRNA processing assays. However, the physiological relevance of heme in miRNA maturation has not been clear. Here, we present a live-cell pri-miRNA processing assay that produces robust signals and faithfully indicates DGCR8 and Drosha activities. We demonstrate that all known heme-binding-deficient DGCR8 mutants are defective in pri-miRNA processing in HeLa cells. DGCR8 contains a previously uncharacterized heme-binding motif, "IPCL," that is also required for its activity. Heme availability and biosynthesis in HeLa cells positively affect pri-miRNA processing and production of mature miRNA. These results establish an essential function for heme in pri-miRNA processing in mammalian cells. Our study suggests that abnormal heme biosynthesis and degradation may contribute to diseases via miRNA-mediated gene regulation networks.

DiGeorge syndrome critical region gene 8 (DGCR8) is the RNA-binding partner protein of the nuclease Drosha. DGCR8 and Drosha recognize and cleave primary transcripts of microRNAs (pri-miRNAs) in the maturation of canonical microRNAs (miRNAs) in animals. We previously reported that human, frog, and starfish DGCR8 bind heme when expressed in Escherichia coli and that Fe(III) heme activates apoDGCR8 in reconstituted pri-miRNA processing assays. However, the physiological relevance of heme in miRNA maturation has not been clear. Here, we present a live-cell pri-miRNA processing assay that produces robust signals and faithfully indicates DGCR8 and Drosha activities. We demonstrate that all known heme-binding-deficient DGCR8 mutants are defective in pri-miRNA processing in HeLa cells. DGCR8 contains a previously uncharacterized heme-binding motif, "IPCL," that is also required for its activity. Heme availability and biosynthesis in HeLa cells positively affect pri-miRNA processing and production of mature miRNA. These results establish an essential function for heme in pri-miRNA processing in mammalian cells. Our study suggests that abnormal heme biosynthesis and degradation may contribute to diseases via miRNA-mediated gene regulation networks.

Objective

Perinatal nicotine exposure alters offspring lung structure and function; however, the underlying mechanisms remain incompletely understood. Whether epithelial-mesenchymal transition (EMT), a known contributor to pulmonary pathology, occurs following moderate perinatal nicotine exposure is not known.

Methods

Pregnant, pair-fed Sprague Dawley rat dams received either placebo (diluent) or nicotine [1 mg/kg, subcutaneously] once daily from embryonic day (e) 6 to postnatal day (PND) 21. Generation 1 (F1) and 3 (F3) offspring lungs were isolated at PND 21, and using Western analysis, q-RT-PCR and immunohistochemistry examined for evidence of EMT. To gain further supportive evidence for nicotine-induced EMT, embryonic day 19 primary rat lung alveolar type II (ATII) cells were cultured and treated with nicotine for 24 hr.

Results

Protein levels of α-smooth muscle actin, fibronectin, and calponin (myogenic differentiation markers) increased significantly. However, surfactant proteins B and C, and cholinephosphate cytidylyltransferase-α (epithelial cell markers), as well as the typical markers of EMT, E-cadherin, N-cadherin, and fibroblast specific protein (FSP)-1, in both F1 and F3 generation lungs, showed no significant change between the nicotine exposed and control dams. Immunostaining of lung sections and data from in vitro treated ATII cells strongly supported the Western data.

Conclusions

Enhanced myogenic molecular profile, without evidence of EMT, as evidenced by the absence of the loss of E-cadherin or gains in N-cadherin and FSP-1, suggest that perinatal nicotine exposure does not result in EMT, but it leads to myogenesis, which predominantly accounts for the lung phenotype seen in perinatally nicotine exposed rat offspring. Pediatr Pulmonol. 2016;51:1142-1150. © 2016 Wiley Periodicals, Inc.

Reported here is the chelate effect as a design principle for tuning heterogeneous catalysts for electrochemical CO₂ reduction. Palladium functionalized with a chelating tris-N-heterocyclic carbene (NHC) ligand (Pd-timtmb^Me ) exhibits a 32-fold increase in activity for electrochemical reduction of CO₂ to C1 products with high Faradaic efficiency (FE_C1 =86 %) compared to the parent unfunctionalized Pd foil (FE=23 %), and with sustained activity relative to a monodentate NHC-ligated Pd electrode (Pd-mimtmb^Me ). The results highlight the contributions of the chelate effect for tailoring and maintaining reactivity at molecular-materials interfaces enabled by surface organometallic chemistry.

Conversion of carbon monoxide (CO), a major one-carbon product of carbon dioxide (CO₂) reduction, into value-added multicarbon species is a challenge to addressing global energy demands and climate change. Here we report a modular synthetic approach for aqueous electrochemical CO reduction to carbon-carbon coupled products via self-assembly of supramolecular cages at molecular-materials interfaces. Heterobimetallic cavities formed by face-to-face coordination of thiol-terminated metalloporphyrins to copper electrodes through varying organic struts convert CO to C2 products with high faradaic efficiency (FE = 83% total with 57% to ethanol) and current density (1.34 mA/cm²) at a potential of -0.40 V vs RHE. The cage-functionalized electrodes offer an order of magnitude improvement in both selectivity and activity for electrocatalytic carbon fixation compared to parent copper surfaces or copper functionalized with porphyrins in an edge-on orientation.

Background

By stimulating lipofibroblast maturation, parenterally administered peroxisome proliferator-activated receptor γ (PPARγ) agonists promote lung homeostasis and injury repair in the neonatal lung. In this study, we determined whether PPARγ agonists could be delivered effectively via nebulization to neonates, and whether this approach would also protect against hyperoxia-induced lung injury.

Methods

One-day old Sprague-Dawley rat pups were administered PPARγ agonists rosiglitazone (RGZ, 3 mg/kg), pioglitazone (PGZ, 3 mg/kg), or the diluent, via nebulization every 24 h; animals were exposed to 21% or 95% O2 for up to 72 h. Twenty-four and 72 h following initial nebulization, the pups were sacrificed for lung tissue and blood collection to determine markers of lung maturation, injury repair, and RGZ and PGZ plasma levels.

Results

Nebulized RGZ and PGZ enhanced lung maturation in both males and females, as evidenced by the increased expression of markers of alveolar epithelial and mesenchymal maturation. This approach also protected against hyperoxia-induced lung injury, since hyperoxia-induced changes in bronchoalveolar lavage cell and protein contents and lung injury markers were all blocked by nebulized PGZ.

Conclusion

Nebulized PPARγ agonist administration promotes lung maturation and prevents neonatal hyperoxia-induced lung injury in both males and females.

Nicotine inhalation via electronic cigarettes (e-cigs) is an emerging concern. However, little is known about the acute toxicity in the lungs following inhalation of nicotine-containing e-cig aerosols. We hypothesized that acute exposure to aerosolized nicotine causes lung toxicity by eliciting inflammatory and dysregulated repair responses. Adult C57BL/6J mice were exposed 2 h daily for 3 days to e-cig aerosols containing propylene glycol (PG) with or without nicotine. Acute exposure to nicotine-containing e-cig aerosols induced inflammatory cell influx (neutrophils and CD8a⁺ T-lymphocytes), and release of pro-inflammatory cytokines in bronchoalveolar lavage fluid in a sex-dependent manner. Inhalation of e-cig aerosol containing PG alone significantly augmented the lung levels of various homeostasis/repair mediators (PPARγ, ADRP, ACTA2, CTNNB1, LEF1, β-catenin, E-cadherin, and MMP2) in a sex-dependent manner when compared to air controls. These findings were accompanied by an increase in protein abundance and altered gene expression of lipogenic markers (PPARγ, ADRP) and myogenic markers (fibronectin, α-smooth muscle actin and β-catenin), suggesting a dysregulated repair response in mouse lungs. Furthermore, exposure to nicotine containing e-cig aerosols or PG alone differentially affected the release of pro-inflammatory cytokines in healthy and COPD human 3D EpiAirway tissues. Overall, acute exposure to nicotine containing e-cig aerosols was sufficient to elicit a pro-inflammatory response and altered mRNA and protein levels of myogenic, lipogenic, and extracellular matrix markers in mouse lung in a sex-dependent manner. Thus, acute exposure to inhaled nicotine via e-cig leads to dysregulated repair and inflammatory responses, which may lead to airway remodeling in the lungs.