scholarly journals Surfactant-associated protein A is important for maintaining surfactant large-aggregate forms during surface-area cycling

1996 ◽  
Vol 313 (3) ◽  
pp. 835-840 ◽  
Author(s):  
Ruud A. W. VELDHUIZEN ◽  
Li-Juan YAO ◽  
Stephen A. HEARN ◽  
Fred POSSMAYER ◽  
James F. LEWIS
Keyword(s):  
Surface Area ◽  
Protein A ◽  
Immunoblot Analysis ◽  
Dependent Manner ◽  
Large Aggregate ◽  
Surfactant Aggregates ◽  
Alveolar Surfactant ◽  
Surface Active

Alveolar surfactant can be separated into two major subfractions, the large surfactant aggregates (LAs) and the small surfactant aggregates (SAs). The surface-active LAs are the metabolic precursors of the inactive SAs. This conversion of LAs into SAs can be studied in vitro using a technique called surface-area cycling. We have utilized this technique to examine the effect of trypsin on aggregate conversion. Our results show that trypsin increases the conversion of LAs into SAs in a concentration- and time-dependent manner. Immunoblot analysis revealed that surfactant-associated Protein A (SP-A) was the main target of trypsin. To examine further the role of SP-A in aggregate conversion, we tested the effect of Ca2+ and mannan on this process. The absence of Ca2+ (1 mM EDTA) and the presence of mannan both increased the formation of SAs. Electron microscopy revealed that highly organized multilamellar and tubular myelin structures were present in samples that converted slowly to SAs. We concluded that SP-A is important for maintaining LA forms during surface-area cycling by stabilizing tubular myelin and multilamellar structures.

scholarly journals Degradation of surfactant-associated protein B (SP-B) during in vitro conversion of large to small surfactant aggregates

1993 ◽  
Vol 295 (1) ◽  
pp. 141-147 ◽  
Author(s):  
R A W Veldhuizen ◽  
K Inchley ◽  
S A Hearn ◽  
J F Lewis ◽  
F Possmayer
Keyword(s):  
Surface Area ◽  
Sucrose Gradient ◽  
Gradient Centrifugation ◽  
Sucrose Gradient Centrifugation ◽  
Aggregate Fraction ◽  
Surfactant Aggregates ◽  
Morphological Studies ◽  
Surface Active ◽  
Protein B

Pulmonary surfactant obtained from lung lavages can be separated by differential centrifugation into two distinct subfractions known as large surfactant aggregates and small surfactant aggregates. The large-aggregate fraction is the precursor of the small-aggregate fraction. The ratio of the small non-surface-active to large surface-active surfactant aggregates increases after birth and in several types of lung injury. We have utilized an in vitro system, surface area cycling, to study the conversion of large into small aggregates. Small aggregates generated by surface area cycling were separated from large aggregates by centrifugation at 40,000 g for 15 min rather than by the normal sucrose gradient centrifugation. This new separation method was validated by morphological studies. Surface-tension-reducing activity of total surfactant extracts, as measured with a pulsating-bubble surfactometer, was impaired after surface area cycling. This impairment was related to the generation of small aggregates. Immunoblot analysis of large and small aggregates separated by sucrose gradient centrifugation revealed the presence of detectable amounts of surfactant-associated protein B (SP-B) in large aggregates but not in small aggregates. SP-A was detectable in both large and small aggregates. PAGE of cycled and non-cycled surfactant showed a reduction in SP-B after surface area cycling. We conclude that SP-B is degraded during the formation of small aggregates in vitro and that a change in surface area appears to be necessary for exposing SP-B to protease activity.

Role of clathrin-mediated endocytosis of surfactant protein A by alveolar macrophages in intracellular signaling

2009 ◽  
Vol 296 (3) ◽  
pp. L430-L441 ◽  
Author(s):  
Christina Moulakakis ◽  
Cordula Stamme
Keyword(s):  
Alveolar Macrophages ◽  
Intracellular Signaling ◽  
Protein A ◽  
Surfactant Protein ◽  
Kinase Assay ◽  
Coated Vesicle ◽  
Dependent Manner ◽  
Tnf Α

We recently provided evidence that anti-inflammatory macrophage activation, i.e., the inhibition of constitutive and signal-induced NF-κB activity by the pulmonary collectin surfactant protein (SP)-A, critically involves a promoted stabilization of IκB-α, the predominant inhibitor of NF-κB, via posttranscriptional mechanisms comprising the activation of atypical (a)PKCζ. SP-A uptake and degradation by alveolar macrophages (AMφ) occur in a receptor-mediated, clathrin-dependent manner. However, a mutual link between endocytosis of and signaling by SP-A remains elusive. The aim of this study was to investigate whether clathrin-mediated endocytosis (CME) of SP-A by AMφ is a prerequisite for its modulation of the IκB-α/NF-κB pathway. The inhibition of clathrin-coated pit (CCP) formation and clathrin-coated vesicle (CCV) formation/budding abrogates SP-A-mediated IκB-α stabilization and SP-A-mediated inhibition of LPS-induced NF-κB activation in freshly isolated rat AMφ, as determined by Western analysis, fluorescence-activated cell sorting, confocal microscopy, and EMSA. Actin depolymerization and inhibition of CCP formation further abolished SP-A-mediated inhibition of LPS-induced TNF-α release, as determined by ELISA. In addition, SP-A-induced atypical PKCζ activation was abolished by pretreatment of AMφ with CCV inhibitors as determined by in vitro immunocomplex kinase assay. Although CME is classically considered as a means to terminate signaling, our results demonstrate that SP-A uptake via CME by AMφ has to precede the initiation of SP-A signaling.

Alveolar surfactant aggregate conversion in ventilated normal and injured rabbits

1996 ◽  
Vol 270 (1) ◽  
pp. L152-L158 ◽  
Author(s):  
R. A. Veldhuizen ◽  
J. Marcou ◽  
L. J. Yao ◽  
L. McCaig ◽  
Y. Ito ◽  
...  
Keyword(s):  
Active Form ◽  
Large Aggregate ◽  
Mechanically Ventilated ◽  
Aggregate Fraction ◽  
Severity Of Injury ◽  
Alveolar Surfactant ◽  
Surface Active ◽  
Intratracheal Injection

Alveolar surfactant can be separated into two subtypes; large aggregates and small aggregates. Large aggregates represent the surface active form of surfactant and are the metabolic precursors of small aggregates. Previous studies examined the mechanism by which large aggregates are converted into small aggregates in vitro. We used intratracheal injection of radiolabeled large aggregates in rabbits to probe the aggregate conversion in vivo. After this injection, animals were mechanically ventilated for 60 min. After the animals were killed, the lungs were lavaged, and the percentage of radiolabel present in the small aggregate fraction was determined. Our results showed that ventilation resulted in aggregate conversion and that increases in tidal volume, but not in respiratory rate, correlated with increased conversion. Aggregate conversion in rabbits with acute lung injury correlated significantly with severity of injury. We conclude that a change in surface area (i.e., respiration) is necessary for aggregate conversion in vivo and that the ventilation strategy can affect this conversion. Furthermore, increased aggregate conversion in injured lungs might contribute to increased small-to-large aggregate ratios in these lungs compared with normal lungs.

scholarly journals Activation of mitochondrial TUFM ameliorates metabolic dysregulation through coordinating autophagy induction

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Dasol Kim ◽  
Hui-Yun Hwang ◽  
Eun Sun Ji ◽  
Jin Young Kim ◽  
Jong Shin Yoo ◽  
...  
Keyword(s):  
Metabolic Regulation ◽  
Elongation Factor ◽  
Dependent Manner ◽  
Diet Induced Obesity ◽  
Metabolic Dysregulation ◽  
Autophagy Induction ◽  
Transcription Factor Eb ◽  
Mitochondrial Elongation

AbstractDisorders of autophagy, a key regulator of cellular homeostasis, cause a number of human diseases. Due to the role of autophagy in metabolic dysregulation, there is a need to identify autophagy regulators as therapeutic targets. To address this need, we conducted an autophagy phenotype-based screen and identified the natural compound kaempferide (Kaem) as an autophagy enhancer. Kaem promoted autophagy through translocation of transcription factor EB (TFEB) without MTOR perturbation, suggesting it is safe for administration. Moreover, Kaem accelerated lipid droplet degradation in a lysosomal activity-dependent manner in vitro and ameliorated metabolic dysregulation in a diet-induced obesity mouse model. To elucidate the mechanism underlying Kaem’s biological activity, the target protein was identified via combined drug affinity responsive target stability and LC–MS/MS analyses. Kaem directly interacted with the mitochondrial elongation factor TUFM, and TUFM absence reversed Kaem-induced autophagy and lipid degradation. Kaem also induced mitochondrial reactive oxygen species (mtROS) to sequentially promote lysosomal Ca2+ efflux, TFEB translocation and autophagy induction, suggesting a role of TUFM in mtROS regulation. Collectively, these results demonstrate that Kaem is a potential therapeutic candidate/chemical tool for treating metabolic dysregulation and reveal a role for TUFM in autophagy for metabolic regulation with lipid overload.

scholarly journals Secreted KIAA1199 promotes the progression of rheumatoid arthritis by mediating hyaluronic acid degradation in an ANXA1-dependent manner

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wei Zhang ◽  
Guoyu Yin ◽  
Heping Zhao ◽  
Hanzhi Ling ◽  
Zhen Xie ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Hyaluronic Acid ◽  
Dependent Manner ◽  
Collagen Induced Arthritis ◽  
Intracellular Degradation ◽  
Main Pathway ◽  
First Time

AbstractIn inflamed joints, enhanced hyaluronic acid (HA) degradation is closely related to the pathogenesis of rheumatoid arthritis (RA). KIAA1199 has been identified as a hyaladherin that mediates the intracellular degradation of HA, but its extracellular function remains unclear. In this study, we found that the serum and synovial levels of secreted KIAA1199 (sKIAA1199) and low-molecular-weight HA (LMW-HA, MW < 100 kDa) in RA patients were significantly increased, and the positive correlation between them was shown for the first time. Of note, treatment with anti-KIAA1199 mAb effectively alleviated the severity of arthritis and reduced serum LMW-HA levels and cytokine secretion in collagen-induced arthritis (CIA) mice. In vitro, sKIAA1199 was shown to mediate exogenous HA degradation by attaching to the cell membrane of RA fibroblast-like synoviosytes (RA FLS). Furthermore, the HA-degrading activity of sKIAA1199 depended largely on its adhesion to the membrane, which was achieved by its G8 domain binding to ANXA1. In vivo, kiaa1199-KO mice exhibited greater resistance to collagen-induced arthritis. Interestingly, this resistance could be partially reversed by intra-articular injection of vectors encoding full-length KIAA1199 instead of G8-deleted KIAA119 mutant, which further confirmed the indispensable role of G8 domain in KIAA1199 involvement in RA pathological processes. Mechanically, the activation of NF-κB by interleukin-6 (IL-6) through PI3K/Akt signaling is suggested to be the main pathway to induce KIAA1199 expression in RA FLS. In conclusion, our study supported the contribution of sKIAA1199 to RA pathogenesis, providing a new therapeutic target for RA by blocking sKIAA1199-mediated HA degradation.

scholarly journals Phaseolin Attenuates Lipopolysaccharide-Induced Inflammation in RAW 264.7 Cells and Zebrafish

Biomedicines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 420
Author(s):  
Su-Jung Hwang ◽  
Ye-Seul Song ◽  
Hyo-Jong Lee
Keyword(s):  
Nitric Oxide ◽  
Nuclear Translocation ◽  
Raw 264.7 Cells ◽  
Network Pharmacology ◽  
Raw 264.7 ◽  
Dependent Manner ◽  
Bioactive Constituents

Kushen (Radix Sophorae flavescentis) is used to treat ulcerative colitis, tumors, and pruritus. Recently, phaseolin, formononetin, matrine, luteolin, and quercetin, through a network pharmacology approach, were tentatively identified as five bioactive constituents responsible for the anti-inflammatory effects of S. flavescentis. However, the role of phaseolin (one of the primary components of S. flavescentis) in the direct regulation of inflammation and inflammatory processes is not well known. In this study, the beneficial role of phaseolin against inflammation was explored in lipopolysaccharide (LPS)-induced inflammation models of RAW 264.7 macrophages and zebrafish larvae. Phaseolin inhibited LPS-mediated production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS), without affecting cell viability. In addition, phaseolin suppressed pro-inflammatory mediators such as cyclooxygenase 2 (COX-2), interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and interleukin-6 (IL-6) in a dose-dependent manner. Furthermore, phaseolin reduced matrix metalloproteinase (MMP) activity as well as macrophage adhesion in vitro and the recruitment of leukocytes in vivo by downregulating Ninjurin 1 (Ninj1), an adhesion molecule. Finally, phaseolin inhibited the nuclear translocation of nuclear factor-kappa B (NF-κB). In view of the above, our results suggest that phaseolin could be a potential therapeutic candidate for the management of inflammation.

scholarly journals PapRIV, a BV-2 microglial cell activating quorum sensing peptide

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yorick Janssens ◽  
Nathan Debunne ◽  
Anton De Spiegeleer ◽  
Evelien Wynendaele ◽  
Marta Planas ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Cell Model ◽  
Dependent Manner ◽  
Communication Signals ◽  
Gram Positive Bacteria ◽  
A Cell ◽  
Gastro Intestinal Tract

AbstractQuorum sensing peptides (QSPs) are bacterial peptides produced by Gram-positive bacteria to communicate with their peers in a cell-density dependent manner. These peptides do not only act as interbacterial communication signals, but can also have effects on the host. Compelling evidence demonstrates the presence of a gut-brain axis and more specifically, the role of the gut microbiota in microglial functioning. The aim of this study is to investigate microglial activating properties of a selected QSP (PapRIV) which is produced by Bacillus cereus species. PapRIV showed in vitro activating properties of BV-2 microglia cells and was able to cross the in vitro Caco-2 cell model and reach the brain. In vivo peptide presence was also demonstrated in mouse plasma. The peptide caused induction of IL-6, TNFα and ROS expression and increased the fraction of ameboid BV-2 microglia cells in an NF-κB dependent manner. Different metabolites were identified in serum, of which the main metabolite still remained active. PapRIV is thus able to cross the gastro-intestinal tract and the blood–brain barrier and shows in vitro activating properties in BV-2 microglia cells, hereby indicating a potential role of this quorum sensing peptide in gut-brain interaction.

scholarly journals Lumican Inhibits Osteoclastogenesis and Bone Resorption by Suppressing Akt Activity

2021 ◽  
Vol 22 (9) ◽  
pp. 4717
Author(s):  
Jin-Young Lee ◽  
Da-Ae Kim ◽  
Eun-Young Kim ◽  
Eun-Ju Chang ◽  
So-Jeong Park ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Bone Formation ◽  
Map Kinases ◽  
Osteoclast Differentiation ◽  
Dependent Manner ◽  
Dual Action ◽  
Dose Dependent ◽  
Resorptive Activity

Lumican, a ubiquitously expressed small leucine-rich proteoglycan, has been utilized in diverse biological functions. Recent experiments demonstrated that lumican stimulates preosteoblast viability and differentiation, leading to bone formation. To further understand the role of lumican in bone metabolism, we investigated its effects on osteoclast biology. Lumican inhibited both osteoclast differentiation and in vitro bone resorption in a dose-dependent manner. Consistent with this, lumican markedly decreased the expression of osteoclastogenesis markers. Moreover, the migration and fusion of preosteoclasts and the resorptive activity per osteoclast were significantly reduced in the presence of lumican, indicating that this protein affects most stages of osteoclastogenesis. Among RANKL-dependent pathways, lumican inhibited Akt but not MAP kinases such as JNK, p38, and ERK. Importantly, co-treatment with an Akt activator almost completely reversed the effect of lumican on osteoclast differentiation. Taken together, our findings revealed that lumican inhibits osteoclastogenesis by suppressing Akt activity. Thus, lumican plays an osteoprotective role by simultaneously increasing bone formation and decreasing bone resorption, suggesting that it represents a dual-action therapeutic target for osteoporosis.

Effects of fetal corticosteroid treatments on postnatal surfactant function in preterm lambs

1995 ◽  
Vol 79 (3) ◽  
pp. 846-851 ◽  
Author(s):  
T. Ueda ◽  
M. Ikegami ◽  
D. Polk ◽  
K. Mizuno ◽  
A. Jobe
Keyword(s):  
Surface Area ◽  
Dynamic Compliance ◽  
Alveolar Space ◽  
Prenatal Treatment ◽  
Ultrasound Guided ◽  
Functional Characteristics ◽  
Arterial Pco2 ◽  
Alveolar Surfactant ◽  
Pool Sizes

Effects of prenatal corticosteroid on the properties of surfactant have not previously been evaluated. A single ultrasound-guided fetal injection with 0.5 mg/kg betamethasone 48 h before delivery of preterm lambs at 134- to 135-days gestation improved oxygenation, lowered the ventilatory pressures required to maintain arterial PCO2 between 30 and 40 Torr and decreased the protein leak of albumin from the intravascular to the alveolar space. This dose of glucocorticoid did not alter surfactant-saturated phosphatidylcholine pool sizes in the airspaces of preterm lambs. However, the treatment changed the characteristics of the surfactant recovered from the ventilated preterm lambs. The in vitro conversion from heavy to light subtype surfactant decreased from 59% for the saline-treated lambs to 37% for the corticosteroid-treated lambs after 180 min of surface area cycling (P < 0.02). Surfactant from the corticosteroid-treated lambs also increased the dynamic compliance of preterm surfactant-deficient rabbits more than did surfactant from the saline-treated lambs (P < 0.05). Prenatal treatment of preterm lambs with betamethasone improved the functional characteristics of surfactant without significant effects on the alveolar surfactant pool sizes.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

Sign in / Sign up

Export Citation Format

Share Document