Genome-wide analysis of the common bean (Phaseolus vulgaris) laccase gene family and its functions in response to abiotic stress.

BACKGROUND: Laccase (LAC) gene family plays a pivotal role in plant lignin biosynthesis and adaptation to various stresses. Limited research has been conducted on laccase genes in common beans. RESULTS: 29 LAC gene family members were identified within the common bean genome, distributed unevenly in 9 chromosomes. These members were divided into 6 distinct subclades by phylogenetic analysis. Further phylogenetic analyses and synteny analyses indicated that considerable gene duplication and loss presented throughout the evolution of the laccase gene family. Purified selection was shown to be the major evolutionary force through Ka / Ks. Transcriptional changes of PvLAC genes under low temperature and salt stress were observed, emphasizing the regulatory function of these genes in such conditions. Regulation by abscisic acid and gibberellins appears to be the case for PvLAC3, PvLAC4, PvLAC7, PvLAC13, PvLAC14, PvLAC18, PvLAC23, and PvLAC26, as indicated by hormone induction experiments. Additionally, the regulation of PvLAC3, PvLAC4, PvLAC7, and PvLAC14 in response to nicosulfuron and low-temperature stress were identified by virus-induced gene silence, which demonstrated inhibition on growth and development in common beans. CONCLUSIONS: The research provides valuable genetic resources for improving the resistance of common beans to abiotic stresses and enhance the understanding of the functional roles of the LAC gene family.

PICKLE and HISTONE DEACETYLASE6 coordinately regulate genes and transposable elements in Arabidopsis.

Chromatin dynamics play essential roles in transcriptional regulation. The chromodomain helicase DNA-binding domain 3 (CHD3) chromatin remodeler PICKLE (PKL) and HISTONE DEACETYLASE6 (HDA6) are required for transcriptional gene silencing, but their coordinated function in gene repression requires further study. Through a genetic suppressor screen, we found that a point mutation at PKL could partially restore the developmental defects of a weak Polycomb repressive complex 1 (PRC1) mutant (ring1a-2 ring1b-3), in which RING1A expression is suppressed by a T-DNA insertion at the promoter. Compared to ring1a-2 ring1b-3, the expression of RING1A is increased, nucleosome occupancy is reduced, and the histone 3 lysine 9 acetylation (H3K9ac) level is increased at the RING1A locus in the pkl ring1a-2 ring1b-3 triple mutant. HDA6 interacts with PKL and represses RING1A expression similarly to PKL genetically and molecularly in the ring1a-2 ring1b-3 background. Furthermore, we show that PKL and HDA6 suppress the expression of a set of genes and transposable elements (TEs) by increasing nucleosome density and reducing H3K9ac. Genome-wide analysis indicated they possibly coordinately maintain DNA methylation as well. Our findings suggest that PKL and HDA6 function together to reduce H3K9ac and increase nucleosome occupancy, thereby facilitating gene/TE regulation in Arabidopsis (Arabidopsis thaliana).

Interface states and optical coupling functionalities in the super-SSH lattices.

We theoretically address the coupling between trimer lattices and reveal the existence of stable multiple edge and interface states. It is shown the superlattice can provides a tunable number of topologically protected edge and interface states depending on the coupling strength and topological phase of the connecting lattices. Dynamics and transport properties of interface states are also investigated, Due to the interference of linear modes with different propagation constants, stable oscillations resulted from the coupling of interface states in finite trimerized waveguide arrays are observed and can give rise to optical coupling functionalities, including directional coupling, beam splitting and beam oscillator.

Integrating analog and digital modes of gene expression at Arabidopsis FLC.

Quantitative gene regulation at the cell population level can be achieved by two fundamentally different modes of regulation at individual gene copies. A 'digital' mode involves binary ON/OFF expression states, with population-level variation arising from the proportion of gene copies in each state, while an 'analog' mode involves graded expression levels at each gene copy. At the Arabidopsis floral repressor FLOWERING LOCUS C (FLC), 'digital' Polycomb silencing is known to facilitate quantitative epigenetic memory in response to cold. However, whether FLC regulation before cold involves analog or digital modes is unknown. Using quantitative fluorescent imaging of FLC mRNA and protein, together with mathematical modeling, we find that FLC expression before cold is regulated by both analog and digital modes. We observe a temporal separation between the two modes, with analog preceding digital. The analog mode can maintain intermediate expression levels at individual FLC gene copies, before subsequent digital silencing, consistent with the copies switching OFF stochastically and heritably without cold. This switch leads to a slow reduction in FLC expression at the cell population level. These data present a new paradigm for gradual repression, elucidating how analog transcriptional and digital epigenetic memory pathways can be integrated.

Exogenous Melatonin Modulates Physiological Response to Nitrogen and Improves Yield in Nitrogen-Deficient Soybean (Glycine max L. Merr.).

Melatonin (MT) is a key plant growth regulator. To investigate its effect at different growth stages on the yield of soybean under nitrogen deficiency, 100 µM MT was applied to soybean supplemented with zero nitrogen (0N), low nitrogen (LN), and control nitrogen (CK) levels, during the plant vegetative growth (V3) and filling (R5) stages. This study revealed that the application of MT mainly enhanced the nitrogen fixation of plants by increasing the root nodule number and provided more substrates for glutamine synthetase (GS) under 0N supply. However, under the LN supply, more ammonium was assimilated through the direct promotion of nitrate reductase (NR) activity by MT. MT enhanced the activity of ammonium-assimilation-related enzymes, such as GOGAT and GDH, and the expression of their coding genes, promoted the synthesis of chlorophyll and amino acids, and increased the photosynthetic capacity under nitrogen deficiency. Exogenous MT directly upregulated the expression of genes involved in the photosynthetic system and stimulated dry-matter accumulation. Thus, MT alleviated the inhibitory effect of nitrogen deficiency on soybean yield. This mitigation effect was better when MT was applied at the V3 stage, and the seed weight per plant increased by 16.69 and 12.20% at 0N and LN levels, respectively. The results of this study provide a new theoretical basis to apply MT in agriculture to improve the resilience of soybean plants to low nitrogen availability.

Genome-wide identification of the B3 gene family in soybean and the response to melatonin under cold stress.

Introduction: Melatonin is a multipotent molecule that exists widely in animals and plants and plays an active regulatory role in abiotic stresses. The B3 superfamily is a ubiquitous transcription factor with a B3 functional domain in plants, which can respond temporally to abiotic stresses by activating defense compounds and plant hormones. Despite the fact that the B3 genes have been studied in a variety of plants, their role in soybean is still unknown. Methods: The regulation of melatonin on cold resistance of soybean and the response of B3 genes to cold stress were investigated by measuring biochemical indexes of soybean. Meanwhile, the genome-wide identification of B3 gene family was conducted in soybean, and B3 genes were analyzed based on phylogeny, motifs, gene structure, collinearity, and cis-regulatory elements analysis. Results: We found that cold stress-induced oxidative stress in soybean by producing excessive reactive oxygen species. However, exogenous melatonin treatment could increase the content of endogenous melatonin and other hormones, including IAA and ABA, and enhance the antioxidative system, such as POD activity, CAT activity, and GSH/GSSG, to scavenge ROS. Furthermore, the present study first revealed that melatonin could alleviate the response of soybean to cold stress by inducing the expression of B3 genes. In addition, we first identified 145 B3 genes in soybean that were unevenly distributed on 20 chromosomes. The B3 gene family was divided into 4 subgroups based on the phylogeny tree constructed with protein sequence and a variety of plant hormones and stress response cis-elements were discovered in the promoter region of the B3 genes, indicating that the B3 genes were involved in several aspects of the soybean stress response. Transcriptome analysis and results of qRT-PCR revealed that most GmB3 genes could be induced by cold, the expression of which was also regulated by melatonin. We also found that B3 genes responded to cold stress in plants by interacting with other transcription factors. Discussion: We found that melatonin regulates the response of soybean to cold stress by regulating the expression of the transcription factor B3 gene, and we identified 145 B3 genes in soybean. These findings further elucidate the potential role of the B3 gene family in soybean to resist low-temperature stress and provide valuable information for soybean functional genomics study.

The mechanisms underlying melatonin improved soybean seedling growth at different nitrogen levels.

To investigate the function of melatonin (MT) on nitrogen uptake and metabolism in soybean, six groups of treatments, with and without 100µM melatonin were conducted at low, normal, and high nitrogen levels (1.5, 7.5, and 15mM, respectively). The related indexes of nitrogen metabolism and the antioxidant system of seedlings were measured and analysed. Results indicated that MT could enhance the level of nitrogen metabolism by upregulating the coding genes of enzymes related to nitrogen metabolism and increasing total nitrogen content, especially under low nitrogen levels. Under high nitrogen conditions, the addition of MT not only accelerated ammonium assimilation and utilisation by enhancing the activity of glutamine synthetase involved in ammonium assimilation, but also reduced the extent of membrane lipid peroxidation to alleviate the degree of damage by improving the activity of antioxidant enzymes. In addition, MT enhanced soybean growth with positive effects in morphological changes at different nitrogen levels, including significantly increased stem diameter, total leaf area, and root nodule number, and biomass accumulation. Finally, biomass accumulation increased under low, normal, and high nitrogen levels by 9.80%, 14.06%, and 11.44%, respectively. The results suggested that MT could enhance the soybean tolerance to low and excessive N treatments.

Effects of Neonatal Caffeine Administration on Vessel Reactivity in Adult Mice.

OBJECTIVE: The effects of neonatal caffeine therapy in adults born preterm are uncertain. We studied the impact of neonatal caffeine on systemic blood pressure, vessel reactivity, and response to stress in adult mice. STUDY DESIGN: Mice pups were randomized to caffeine (20 mg/kg/d) or saline by intraperitoneal injection for 10 days after birth. We performed tail-cuff BP (8/12 weeks), urinary 8-hydroxydeoxyguanosine and fecal corticosterone (14 weeks), and vessel reactivity in aortic rings (16 weeks) in adult mice. RESULTS: No differences were noted in systolic, diastolic, and mean blood pressures between the two groups at 8 and 12 weeks of age. However, norepinephrine-induced vasoconstriction was substantially higher in aortic rings in CAF-treated male mice. More significant vasodilator responses to nitric oxide donors in aortic rings in female mice may suggest gender-specific effects of caffeine. Female mice exposed to caffeine had significantly lower body weight over-time. Caffeine-treated male mice had substantially higher fecal corticosterone and urinary 8-hydroxydeoxyguanosine at 14 weeks, suggestive of chronic stress. CONCLUSION: We conclude sex-specific vulnerability to the heightened vascular tone of the aorta in male mice following neonatal caffeine therapy. Altered vessel reactivity and chronic stress in the presence of other risk factors may predispose to the development of systemic hypertension in adults born preterm.

Short-term perinatal oxygen exposure may impair lung development in adult mice.

BACKGROUND: Hyperoxia at resuscitation increases oxidative stress, and even brief exposure to high oxygen concentrations during stabilization may trigger organ injury with adverse long-term outcomes in premature infants. We studied the long-term effects of short-term perinatal oxygen exposure on cell cycle gene expression and lung growth in adult mice. METHODS: We randomized mice litters at birth to 21, 40, or 100%O2 for 30 min and recovered in room air for 4 or 12 weeks. Cell cycle gene expression, protein analysis, and lung morphometry were assessed at 4 and 12 weeks. RESULTS: The principal component analysis demonstrated a high degree of correlation for cell cycle gene expression among the three oxygen groups. Lung elastin was significantly lower in the 100%O2 groups at 4 weeks. On lung morphometry, radial alveolar count, alveolar number, and septal count were similar. However, the mean linear intercept (MLI) and septal length significantly correlated among the oxygen groups. The MLI was markedly higher in the 100%O2 groups at 4 and 12 weeks of age, and the septal length was significantly lower in the 100%O2 groups at 12 weeks. CONCLUSION: Short-term exposure to high oxygen concentrations lead to subtle changes in lung development that may affect alveolarization. The changes are related explicitly to secondary crest formation that may result in alteration in lung elastin. Resuscitation with high oxygen concentrations may have a significant impact on lung development and long-term outcomes such as BPD in premature infants.

Antioxidant MnTBAP does not protect adult mice from neonatal hyperoxic lung injury.

BACKGROUND: Oxygen therapy and mechanical ventilation are important predisposing factors for the development of bronchopulmonary dysplasia (BPD), leading to increased morbidity and mortality in premature infants. Oxygen toxicity mediated by reactive oxygen species (ROS) may play an important part in the development of BPD. We studied the effects of MnTBAP, a catalytic antioxidant on airway responsiveness and alveolar simplification in adult mice following neonatal hyperoxia. METHODS: Mice litters were randomized to 85 %O2 or room air (RA) on D3 for 12 days to receive either MnTBAP (10 mg/kg/d) or saline intraperitoneally. Methacholine challenge (MCC) performed at 8 and 12 weeks of age by whole-body plethysmography to assess airway reactivity. Alveolarization quantified on lung sections by radial alveolar count (RAC) and mean linear intercept (MLI). Cell counts assessed from bronchoalveolar lavage (BAL) performed at 15 weeks. RESULTS: Mice exposed to hyperoxia and MnTBAP (OXMN) had significantly higher airway reactivity post-MCC at 8 weeks compared to RA and O2 groups. At 12 weeks, airway reactivity was higher post-MCC in both hyperoxia and OXMN groups. MnTBAP did not attenuate hyperoxia-induced airway reactivity in adult mice. Hyperoxia exposed mice demonstrated large and distended alveoli on histopathology at 2 and 15 weeks. MnTBAP did not ameliorate hyperoxia-induced lung injury as assessed by RAC/MLI. Absolute lymphocyte count was significantly higher in BAL in the hyperoxia and OXMN groups. CONCLUSIONS: MnTBAP, a catalytic antioxidant, did not afford protection from hyperoxia-induced lung injury in adult mice.

Pumping up the charge density of a triboelectric nanogenerator by charge-shuttling.

As an emerging technology for harvesting mechanical energy, low surface charge density greatly hinders the practical applications of triboelectric nanogenerators (TENGs). Here, a high-performance TENG based on charge shuttling is demonstrated. Unlike conventional TENGs with static charges fully constrained on the dielectric surface, the device works based on the shuttling of charges corralled in conduction domains. Driven by the interaction of two quasi-symmetrical domains, shuttling of two mirror charge carriers can be achieved to double the charge output. Based on the mechanism, an ultrahigh projected charge density of 1.85 mC m-2 is obtained in ambient conditions. An integrated device for water wave energy harvesting is also presented, confirming its feasibility for practical applications. The device provides insights into new modes of TENGs using unfixed charges in domains, shedding a new light on high-performance mechanical energy harvesting technology.

Phosphatase and tensin homolog deletion enhances neurite outgrowth during neural stem cell differentiation.

Neural stem cell (NSC) transplantation has emerged as a promising approach for the treatment of neurological disorders such as cerebral ischemia. As the majority of newly generated cells from exogenous NSCs fail to integrate into the ischemic brain and establish functional synaptic networks, NSC transplantation for ischemic stroke experiences limited neurological function recovery. Augment of endogenous neurite growth in the process of NSC differentiation is an avenue to promote synaptic networks. Phosphatase and tensin homolog (PTEN), a tumor suppressor, has been established to regulate axon growth in the adult central nervous system. The aim of this study was to explore the role of PTEN on neurite growth during NSC differentiation. Our results revealed that the protein expression of PTEN was significantly increased during NSC differentiation, whereas the expression of phosphorylated S6 ribosomal (p-S6R) was markedly decreased. Small interfering RNA knockdown of PTEN in NSCs can accelerate neurite outgrowth during NSC differentiation. These results indicated a remarkable effect of PTEN inhibition on neuronal process after NSC differentiation, and identified a novel route to promote endogenous neurite growth in differentiated NSCs, which may facilitate the application of NSC transplantation in ischemic stroke.

Short-term perinatal oxygen exposure may impair lung development in adult mice

BACKGROUND: Hyperoxia at resuscitation increases oxidative stress, and even brief exposure to high oxygen concentrations during stabilization may trigger organ injury with adverse long-term outcomes in premature infants. We studied the long-term effects of short-term perinatal oxygen exposure on cell cycle gene expression and lung growth in adult mice. METHODS: We randomized mice litters at birth to 21,40, or 100%O2 for 30 min and recovered in room air for 4 or 12 weeks. Cell cycle gene expression, protein analysis, and lung morphometry were assessed at 4 and 12 weeks. RESULTS: The principal component analysis demonstrated a high degree of correlation for cell cycle gene expression among the three oxygen groups. Lung elastin was significantly lower in the 100%O2 groups at 4 weeks. On lung morphometry, radial alveolar count, alveolar number, and septal count were similar. However, the mean linear intercept (MLI) and septal length significantly correlated among the oxygen groups. The MLI was markedly higher in the 100%O2 groups at 4 and 12 weeks of age, and the septal length was significantly lower in the 100%O2 groups at 12 weeks. CONCLUSION: Short-term exposure to high oxygen concentrations lead to subtle changes in lung development that may affect alveolarization. The changes are related explicitly to secondary crest formation that may result in alteration in lung elastin. Resuscitation with high oxygen concentrations may have a significant impact on lung development and long-term outcomes such as BPD in premature infants.

Caffeine is associated with improved alveolarization and angiogenesis in male mice following hyperoxia induced lung injury.

BACKGROUND: Caffeine therapy for apnea of prematurity reduces the incidence of bronchopulmonary dysplasia (BPD) in premature neonates. Several mechanisms, including improvement in pulmonary mechanics underly beneficial effects of caffeine in BPD. As vascular development promotes alveologenesis, we hypothesized that caffeine might enhance angiogenesis in the lung, promoting lung growth, thereby attenuating BPD. METHODS: C57Bl/6 mice litters were randomized within 12 h of birth to room air (RA) or 95%O2 to receive caffeine (20 mg/kg/day) or placebo for 4 days and recovered in RA for 12wks. The lung mRNA and protein expression for hypoxia-inducible factors (HIF) and angiogenic genes performed on day 5. Lung morphometry and vascular remodeling assessed on inflation fixed lungs at 12wks. RESULTS: Caffeine and hyperoxia in itself upregulate HIF-2α and vascular endothelial growth factor gene expression. Protein expression of HIF-2α and VEGFR1 were higher in hyperoxia/caffeine and angiopoietin-1 lower in hyperoxia. An increase in radial alveolar count, secondary septal count, and septal length with a decrease in mean linear intercept indicate an amelioration of hyperoxic lung injury by caffeine. An increase in vessel surface area and a significant reduction in smooth muscle thickness of the pulmonary arterioles may suggest a beneficial effect of caffeine on vascular remodeling in hyperoxia, especially in male mice. CONCLUSIONS: Postnatal caffeine by modulating angiogenic gene expression early in lung development may restore the pulmonary microvasculature and alveolarization in adult lung.

The Impacts of Peptic Ulcer on Functional Outcomes of Ischemic Stroke.

BACKGROUND AND PURPOSE: Studies have shown that peptic ulcer increased the risk of ischemic stroke and stroke recurrence. This study aimed to evaluate the impacts of peptic ulcer on functional outcomes of ischemic stroke. METHODS: Patients with first-ever ischemic stroke were grouped as with and without history of peptic ulcer. Functional outcomes were evaluated with modified Rankin scale at 90 days after the index stroke. Favorable functional outcomes were defined as with a modified Rankin scale score of 0-2. Logistic regression was used to identify predictors for favorable functional outcomes at 90 days. RESULTS: Among the 2577 enrolled patients with ischemic stroke, 129 (5.0%) had a history of peptic ulcer. The proportion of favorable outcome was higher in patients without peptic ulcer than those with (59.3% versus 42.6%, P < .001). Multivariate logistic analysis detected that history of peptic ulcer (odds ratio [OR] = 2.89, 95% confidence interval [CI], 1.03-8.10, P = .043), National Institute of Health Stroke Scale score (OR = 2.11, 95% CI, 1.79-2.48, P < .001), and large-artery atherosclerosis stroke subtype (OR = 4.08, 95% CI, 1.11-15.03, P = .035) decreased the likelihood of favorable outcomes. CONCLUSIONS: Ischemic stroke patients with peptic ulcer may have an increased risk of less favorable neurological outcome at 90 days after the index stroke.

Tumor microenvironment-manipulated radiocatalytic sensitizer based on bismuth heteropolytungstate for radiotherapy enhancement.

Radioresistance resulted from the intrinsic features of tumors often gives rise to unsatisfied therapeutic outcome. In particular, the tumor microenvironment (TME) with abundant antioxidants, elevated hydrogen peroxide (H2O2) and hypoxia has been believed as a tremendous obstacle for radiotherapy. Therefore, developing an effective radiosensitizer in response to both X-ray and the TME is highly imperative but remains a challenge so far. Here, we for the first time explore bismuth heteropolytungstate (BiP5W30) nanoclusters as radiosensitizers for the TME-manipulated enhancement of radiotherapy. On the one hand, BiP5W30 nanoclusters can increase radiation dose deposition within tumors by high-Z elements like Bi and W. On the other hand, in virtue of the unique electron structure and multi-electron property, they have the capability of depleting glutathione (GSH) via redox reaction and catalyzing the decomposition of H2O2 to HO to enhance ROS generation upon X-ray radiation. Moreover, reduced graphene oxide (rGO) coupled with BiP5W30 can further improve radiocatalytic activity through promoting electron-hole separation. Simultaneously, due to the considerable near-infrared absorption of rGO, photothermal therapy can overcome the tumor hypoxia microenvironment and thus synergize with radiotherapy. In addition to providing a promising radiosensitizer, this finding is expected to extend the application of polyoxometalates used in the biomedical field.

Adaptive immune responses are altered in adult mice following neonatal hyperoxia.

Premature infants with bronchopulmonary dysplasia (BPD), are at risk for frequent respiratory infections and reduced pulmonary function. We studied whether neonatal hyperoxia disrupts adaptive immune responses in adult mice, contributing to higher respiratory-related morbidities seen in these infants. Newborn mice litters were randomized at 3 days to 85% O2 or room air (RA) for 12 days. Whole lung mRNA was isolated in both the groups at 2 weeks and 3 months. Gene expression for T-cell and B-cell adaptive immune response was performed by real-time PCR and qRT-PCR; protein expression (p21, IL4, IL10, IL27, cd4) was performed by enzyme immunoassay along with p21 immunohistochemistry. Hyperoxia increased expression of p21 and decreased expression of 19 genes representing T/B-cell activation by ≥ fourfold; three of them significantly (Rag1, Cd1d1, Cd28) compared to the RA group at 2 weeks. Despite RA recovery, the expression of IFNγ, IL27, and CD40 was significantly reduced at 3 months in the hyperoxia group. Expression of p21 was significantly higher and IL27 protein lower at 2 weeks following hyperoxia. Adult mice exposed to neonatal hyperoxia had lower IL4 and IL10 in the lung at 3 months. Adaptive immune responses are developmentally regulated and neonatal hyperoxia suppresses expression of genes involved in T-/B-cell activation with continued alterations in gene expression at 3 months. Dysfunction of adaptive immune responses increases the risk for susceptibility to infection in premature infants.

Long-Term Effects of Neonatal Hyperoxia in Adult Mice.

The outcomes of premature infants have improved greatly; however, the health risks in adulthood are still relatively unclear. Bronchopulmonary dysplasia (BPD) in premature infants is a major risk factor for alteration in lung function and predisposition to respiratory morbidity, and is associated with hyperoxia. The study explores the effect of neonatal hyperoxia on organ systems in adult mice. Newborn mouse litters were randomized to 85%O2 or room air (RA) on P3 for 12 days; mice were sacrificed at P3, P7, P15, 3 months and 9 months. Lungs were assessed by histopathology, radial alveolar count, mean linear intercept, and α-Smooth muscle actin immunohistochemistry. Aortic assessment included histology, wall thickness, elastin, and collagen content. Glomerular histology and nephron number were assessed in the kidneys. Hyperoxia-exposed mice had progressive alveolar simplification and poor weight gain over time. Greater thickness of pulmonary arterioles by 3 months and a higher Fulton index by 9 months suggest worsening pulmonary hypertension. Aortic wall thickness to lumen ratio was greater with a lower aortic elastin-to-collagen ratio suggesting long-term effects of neonatal hyperoxia. Hyperoxia-exposed mice at 9 months had smaller glomeruli as indicated by glomerular diameter and volume. Prolonged neonatal hyperoxia during the critical period of development induces irreversible lung damage, pulmonary hypertension and structural changes in the kidneys and aorta in adult mice. This could have implications for chronic adult diseases following exposure to high levels of oxygen in the newborn period. Anat Rec, 301:717-726, 2018. © 2017 Wiley Periodicals, Inc.

Nfib hemizygous mice are protected from hyperoxic lung injury and death.

Nuclear Factor I (Nfi) genes encode transcription factors essential for the development of organ systems including the lung. Nfib null mice die at birth with immature lungs. Nfib hemizygous mice have reduced lung maturation with decreased survival. We therefore hypothesized that these mice would be more sensitive to lung injury and would have lower survival to hyperoxia. Adult Nfib hemizygous mice and their wild-type (Wt) littermates were exposed to 100% O2 for 89, 80, 72 and 66 h for survival studies with lung outcome measurements at 66 h. Nfib hemizygous and Wt controls were also studied in RA at 66 h. Cell counts and cytokines were measured in bronchoalveolar lavage (BAL); lung sections examined by histopathology; lung angiogenic and oxidative stress gene expression assessed by real-time PCR Unexpectedly, Nfib hemizygous mice (0/14-0%) had significantly lower mortality compared to Wt mice (10/22-45%) at 80 h of hyperoxia (P < 0.003). LD50 was 80 h in the Wt group versus 89 h in the hemizygous group. There were no differences in BAL cell counts between the groups. Among the cytokines studied, MIP-2 was significantly lower in hemizygous mice exposed to hyperoxia. New vessel formation, edema, congestion, and alveolar hemorrhage were noted on histopathology at 72 and 80 h in wild-type mice. Nfib hemizygous lungs had significant downregulation of genes involved in redox signaling and inflammatory pathways. Adult Nfib hemizygous mice are relatively resistant to hyperoxia compared to wild-type littermates. Mechanisms contributing to this resistance are not clear; however, transcription factors such as Nfib may regulate cell survival and play a role in modulating postnatal lung development.

Natriuretic peptide C receptor in the developing sheep lung: role in perinatal transition.

Background: At birth, the release of surfactant from alveolar type II cells (ATIIs) is stimulated by increased activity of the beta-adrenergic/adenylyl cyclase/cyclic 3'-5' adenosine monophosphate-signaling cascade. Atrial natriuretic peptide (ANP) stimulates surfactant secretion through natriuretic peptide receptor A (NPR-A). ANP inhibits adenylyl cyclase activity through its binding to NPR-C. We wished to further understand the role of the NPR-C in perinatal transition. Methods: We studied ATII expression of NPR-C in fetal and newborn sheep using immunohistochemistry, and surfactant secretion in isolated ATIIs by measuring 3[H] choline release into the media. Results: ANP induced surfactant secretion, and, at higher doses, it inhibits the stimulatory effect of the secretagogue terbutaline. ATII NPR-C expression decreased significantly after birth. Premature delivery also markedly decreased ANP and NPR-C in ATIIs. Co-incubation of terbutaline (10-4 M) with ANP (10-6 M) significantly decreased 3[H] choline release from isolated newborn ATII cells when compared with terbutaline alone; this inhibitory effect was mimicked by the specific NPR-C agonist, C-ANP (10-10 M). Conclusion: ANP may act as an important epithelial-derived inhibitor of surfactant release in the fetal lung, and downregulation of ANP and NPR-C following birth may sensitize ATII cells to the effects of circulating catecholamines, thus facilitating surfactant secretion.