| 1. |
- Hansson, Björn, et al.
(författare)
-
Adipose cell size changes are associated with a drastic actin remodeling
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Adipose tissue plays a major role in regulating whole-body insulin sensitivity and energy metabolism. To accommodate surplus energy, the tissue rapidly expands by increasing adipose cell size (hypertrophy) and cell number (hyperplasia). Previous studies have shown that enlarged, hypertrophic adipocytes are less responsive to insulin, and that adipocyte size could serve as a predictor for the development of type 2 diabetes. In the present study, we demonstrate that changes in adipocyte size correlate with a drastic remodeling of the actin cytoskeleton. Expansion of primary adipocytes following 2 weeks of high-fat diet (HFD)-feeding in C57BL6/J mice was associated with a drastic increase in filamentous (F)-actin as assessed by fluorescence microscopy, increased Rho-kinase activity, and changed expression of actin-regulating proteins, favoring actin polymerization. At the same time, increased cell size was associated with impaired insulin response, while the interaction between the cytoskeletal scaffolding protein IQGAP1 and insulin receptor substrate (IRS)-1 remained intact. Reversed feeding from HFD to chow restored cell size, insulin response, expression of actin-regulatory proteins and decreased the amount of F-actin filaments. Together, we report a drastic cytoskeletal remodeling during adipocyte expansion, a process which could contribute to deteriorating adipocyte function.
|
|
| 2. |
- Bagher, Mariam, et al.
(författare)
-
Crosstalk between mast cells and lung fibroblasts is modified by alveolar extracellular matrix and influences epithelial migration
- 2021
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 22:2
-
Tidskriftsartikel (refereegranskat)abstract
- Mast cells play an important role in asthma, however, the interactions between mast cells, fibroblasts and epithelial cells in idiopathic pulmonary fibrosis (IPF) are less known. The objectives were to investigate the effect of mast cells on fibroblast activity and migration of epithelial cells. Lung fibroblasts from IPF patients and healthy individuals were co-cultured with LAD2 mast cells or stimulated with the proteases tryptase and chymase. Human lung fibroblasts and mast cells were cultured on cell culture plastic plates or decellularized human lung tissue (scaffolds) to create a more physiological milieu by providing an alveolar extracellular matrix. Released mediators were analyzed and evaluated for effects on epithelial cell migration. Tryptase increased vascular endothelial growth factor (VEGF) release from fibroblasts, whereas co-culture with mast cells increased IL-6 and hepatocyte growth factor (HGF). Culture in scaffolds increased the release of VEGF compared to culture on plastic. Migration of epithelial cells was reduced by IL-6, while HGF and conditioned media from scaffold cultures promoted migration. In conclusion, mast cells and tryptase increased fibroblast release of mediators that influenced epithelial migration. These data indicate a role of mast cells and tryptase in the interplay between fibroblasts, epithelial cells and the alveolar extracellular matrix in health and lung disease.
|
|
| 3. |
- Hansson, Björn, et al.
(författare)
-
Intact glucose uptake despite deteriorating signaling in adipocytes with high-fat feeding
- 2018
-
Ingår i: Journal of Molecular Endocrinology. - 0952-5041. ; 60:3, s. 199-211
-
Tidskriftsartikel (refereegranskat)abstract
- To capture immediate cellular changes during diet-induced expansion of adipocyte cell volume and number, we characterized mature adipocytes during a short-term high-fat diet (HFD) intervention. Male C57BL6/J mice were fed chow diet, and then switched to HFD for 2, 4, 6 or 14 days. Systemic glucose clearance was assessed by glucose tolerance test. Adipose tissue was dissected for RNA-seq and cell size distribution analysis using coulter counting. Insulin response in isolated adipocytes was monitored by glucose uptake assay and Western blotting, and confocal microscopy was used to assess autophagic activity. Switching to HFD was accompanied by an immediate adipocyte size expansion and onset of systemic insulin resistance already after two days, followed by recruitment of new adipocytes. Despite an initially increased non-stimulated and preserved insulin-stimulated glucose uptake, we observed a decreased phosphorylation of insulin receptor substrate-1 (IRS-1) and protein kinase B (PKB). After 14 days of HFD, both the insulin-stimulated phosphorylation of Akt substrate of 160 kDa (AS160) and glucose uptake was blunted. RNA-seq analysis of adipose tissue revealed transient changes in gene expression at day four, including highly significant upregulation of Trp53inp, previously demonstrated to be involved in autophagy. We confirmed increased autophagy, measured as an increased density of LC3-positive puncta and decreased p62 expression after 14 days of HFD. In conclusion, HFD rapidly induced systemic insulin resistance, whereas insulin-stimulated glucose uptake remained intact throughout 6 days of HFD feeding. We also identified autophagy as an early cellular process that potentially influences adipocyte function upon switching to HFD.
|
|
| 4. |
- Hansson, Björn, et al.
(författare)
-
Rosiglitazone drives cavin-2/SDPR expression in adipocytes in a CEBPα-dependent manner
- 2017
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:3
-
Tidskriftsartikel (refereegranskat)abstract
- Caveolae are abundant adipocyte surface domains involved in insulin signaling, membrane trafficking and lipid homeostasis. Transcriptional control mechanisms for caveolins and cavins, the building blocks of caveolae, are thus arguably important for adipocyte biology and studies in this area may give insight into insulin resistance and diabetes. Here we addressed the hypothesis that one of the less characterized caveolar components, cavin-2 (SDPR), is controlled by CCAAT/Enhancer Binding Protein (CEBPα) and Peroxisome Proliferator- Activated Receptor Gamma (PPARG). Using human mRNA expression data we found that SDPR correlated with PPARG in several tissues. This was also observed during differentiation of 3T3-L1 fibroblasts into adipocytes. Treatment of 3T3-L1-derived adipocytes with the PPARγ-activator Rosiglitazone increased SDPR and CEBPα expression at both the mRNA and protein levels. Silencing of CEBPα antagonized these effects. Further, adenoviral expression of PPARγ/CEBPα or Rosiglitazone-treatment increased SDPR expression in primary rat adipocytes. The myocardin family coactivator MKL1 was recently shown to regulate SDPR expression in human coronary artery smooth muscle cells. However, we found that actin depolymerization, known to inhibit MKL1 and MKL2, was without effect on SDPR mRNA levels in adipocytes, even though overexpression of MKL1 and MKL2 had the capacity to increase caveolins and cavins and to repress PPARγ/CEBPα. Altogether, this work demonstrates that CEBPα expression and PPARγ-activity promote SDPR transcription and further supports the emerging notion that PPARγ/CEBPα and MKL1/MKL2 are antagonistic in adipocytes.
|
|
| 5. |
- Henriksson, Emma, et al.
(författare)
-
SIK2 regulates CRTCs, HDAC4 and glucose uptake in adipocytes
- 2015
-
Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 128:3, s. 472-486
-
Tidskriftsartikel (refereegranskat)abstract
- Salt-inducible kinase 2 (SIK2) is an AMP-activated protein kinase (AMPK) related kinase abundantly expressed in adipose tissue. Our aim was to identify molecular targets and functions of SIK2 in adipocytes, and to address the role of PKA-mediated phosphorylation of SIK2 on Ser358. Modulation of SIK2 in adipocytes resulted in altered phosphorylation of CREB-regulated transcription co-activator 2 (CRTC2), CRTC3 and class IIa histone deacetylase 4 (HDAC4). Furthermore, CRTC2, CRTC3, HDAC4 and protein phosphatase 2A (PP2A) interacted with SIK2, and the binding of CRTCs and PP2A to wild-type but not Ser358Ala SIK2, was reduced by cAMP elevation. Silencing of SIK2 resulted in reduced GLUT4 (also known as SLC2A4) protein levels, whereas cells treated with CRTC2 or HDAC4 siRNA displayed increased levels of GLUT4. Overexpression or pharmacological inhibition of SIK2 resulted in increased and decreased glucose uptake, respectively. We also describe a SIK2-CRTC2-HDAC4 pathway and its regulation in human adipocytes, strengthening the physiological relevance of our findings. Collectively, we demonstrate that SIK2 acts directly on CRTC2, CRTC3 and HDAC4, and that the cAMP-PKA pathway reduces the interaction of SIK2 with CRTCs and PP2A. Downstream, SIK2 increases GLUT4 levels and glucose uptake in adipocytes.
|
|
| 6. |
- Lindahl, Maria, et al.
(författare)
-
ApoA-I Milano stimulates lipolysis in adipose cells independently of cAMP/PKA activation.
- 2015
-
Ingår i: Journal of Lipid Research. - 1539-7262. ; 56:12, s. 2248-2259
-
Tidskriftsartikel (refereegranskat)abstract
- ApoA-I, the main protein component of high-density lipoprotein (HDL), is suggested to be involved in metabolic homeostasis. We examined the effects of Milano, a naturally occurring ApoA-I variant, about which little mechanistic information is available. Remarkably, high fat-fed mice treated with Milano displayed a rapid weight loss greater than ApoA-I WT treated mice, and a significantly reduced adipose tissue mass, without an inflammatory response. Further, lipolysis in adipose cells isolated from mice treated with either WT or Milano was increased. In primary rat adipose cells, Milano stimulated cholesterol efflux and increased glycerol release, independently of β-adrenergic stimulation and phosphorylation of hormone sensitive lipase (Ser563) and perilipin (Ser522). Stimulation with Milano had a significantly greater effect on glycerol release compared with WT but similar effect on cholesterol efflux. Pharmacological inhibition or siRNA silencing of ABCA-1 did not diminish Milano-stimulated lipolysis, although binding to the cell surface was decreased, as analyzed by fluorescence microscopy. Interestingly, methyl-β-cyclodextrin, a well-described cholesterol acceptor, dose-dependently stimulated lipolysis. Together, these results suggest that decreased fat mass and increased lipolysis following Milano treatment in vivo is partly explained by a novel mechanism at the adipose cell level comprising stimulation of lipolysis independently of the canonical cAMP/PKA signaling pathway.
|
|
| 7. |
- Negoita, Florentina, et al.
(författare)
-
PNPLA3 variant M148 causes resistance to starvation-mediated lipid droplet autophagy in human hepatocytes
- 2019
-
Ingår i: Journal of Cellular Biochemistry. - : Wiley. - 0730-2312 .- 1097-4644. ; 120:1, s. 343-356
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanism of how patatin-like phospholipase domain-containing protein 3 (PNPLA3) variant M148 is associated with increased risk of development of hepatic steatosis is still debated. Here, we propose a novel role of PNPLA3 as a key player during autophagosome formation in the process of lipophagy. A human hepatocyte cell line, HepG2 cells, expressing recombinant I148 or 148M, was used to study lipophagy under energy deprived conditions, and lipid droplet morphology was investigated using florescence microscopy, image analysis and biochemical assays. Autophagic flux was studied using the golden-standard of LC3-II turnover in combination with the well characterized GFP-RFP-LC3 vector. To discriminate between, perturbed autophagic initiation and lysosome functionality, lysosomes were characterized by Lysotracker staining and LAMP1 protein levels as well as activity and activation of cathepsin B. For validation, human liver biopsies genotyped for I148 and 148M were analyzed for the presence of LC3-II and PNPLA3 on lipid droplets. We show that the M148-PNPLA3 variant is associated with lipid droplets that are resistant to starvation-mediated degradation. M148 expressing hepatocytes reveal decreased autophagic flux and reduced lipophagy. Both I148-PNPLA3 and M148-PNPLA3 colocalize and interact with LC3-II, but the M148-PNPLA3 variant has lower ability to bind LC3-II. Together, our data indicate that PNPLA3 might play an essential role in lipophagy in hepatocytes and furthermore that the M148-PNPLA3 variant appears to display a loss in this activity, leading to decreased lipophagy.
|
|
| 8. |
- Puthia, Manoj, et al.
(författare)
-
Bioactive Suture with Added Innate Defense Functionality for the Reduction of Bacterial Infection and Inflammation
- 2023
-
Ingår i: Advanced healthcare materials. - 2192-2659. ; 12:31
-
Tidskriftsartikel (refereegranskat)abstract
- Surgical site infections (SSI) are a clinical and economic burden. Suture-associated SSI may develop when bacteria colonize the suture surface and form biofilms that are resistant to antibiotics. Thrombin-derived C-terminal peptide (TCP)-25 is a host defense peptide with a unique dual mode of action that can target both bacteria and the excessive inflammation induced by bacterial products. The peptide demonstrates therapeutic potential in preclinical in vivo wound infection models. In this study, the authors set out to explore whether TCP-25 can provide a new bioactive innate immune feature to hydrophilic polyglactin sutures (Vicryl). Using a combination of biochemical, biophysical, antibacterial, biofilm, and anti-inflammatory assays in vitro, in silico molecular modeling studies, along with experimental infection and inflammation models in mice, a proof-of-concept that TCP-25 can provide Vicryl sutures with a previously undisclosed host defense capacity, that enables targeting of bacteria, biofilms, and the accompanying inflammatory response, is shown.
|
|
| 9. |
- Puthia, Manoj, et al.
(författare)
-
Bioactive Suture with Added Innate Defense Functionality for the Reduction of Bacterial Infection and Inflammation
- 2023
-
Ingår i: Advanced Healthcare Materials. - : Wiley. - 2192-2640 .- 2192-2659. ; 12:31, s. 1-20
-
Tidskriftsartikel (refereegranskat)abstract
- Surgical site infections (SSI) are a clinical and economic burden. Suture-associated SSI may develop when bacteria colonize the suture surface and form biofilms that are resistant to antibiotics. Thrombin-derived C-terminal peptide (TCP)-25 is a host defense peptide with a unique dual mode of action that can target both bacteria and the excessive inflammation induced by bacterial products. The peptide demonstrates therapeutic potential in preclinical in vivo wound infection models. In this study, the authors set out to explore whether TCP-25 can provide a new bioactive innate immune feature to hydrophilic polyglactin sutures (Vicryl). Using a combination of biochemical, biophysical, antibacterial, biofilm, and anti-inflammatory assays in vitro, in silico molecular modeling studies, along with experimental infection and inflammation models in mice, a proof-of-concept that TCP-25 can provide Vicryl sutures with a previously undisclosed host defense capacity, that enables targeting of bacteria, biofilms, and the accompanying inflammatory response, is shown.
|
|
| 10. |
- Schlimpert, Susan, et al.
(författare)
-
Two dynamin-like proteins stabilize FtsZ rings during Streptomyces sporulation
- 2017
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 114:30, s. 6176-6183
-
Tidskriftsartikel (refereegranskat)abstract
- During sporulation, the filamentous bacteria Streptomyces undergo a massive cell division event in which the synthesis of ladders of sporulation septa convert multigenomic hyphae into chains of unigenomic spores. This process requires cytokinetic Z-rings formed by the bacterial tubulin homolog FtsZ, and the stabilization of the newly formed Z-rings is crucial for completion of septum synthesis. Here we show that two dynamin-like proteins, DynA and DynB, play critical roles in this process. Dynamins are a family of large, multidomain GTPases involved in key cellular processes in eukaryotes, including vesicle trafficking and organelle division. Many bacterial genomes encode dynamin-like proteins, but the biological function of these proteins has remained largely enigmatic. Using a cell biological approach, we show that the two Streptomyces dynamins specifically localize to sporulation septa in an FtsZ-dependent manner. Moreover, dynamin mutants have a cell division defect due to the decreased stability of sporulation-specific Z-rings, as demonstrated by kymographs derived from time-lapse images of FtsZ ladder formation. This defect causes the premature disassembly of individual Z-rings, leading to the frequent abortion of septum synthesis, which in turn results in the production of long spore-like compartments with multiple chromosomes. Two-hybrid analysis revealed that the dynamins are part of the cell division machinery and that they mediate their effects on Z-ring stability during developmentally controlled cell division via a network of protein–protein interactions involving DynA, DynB, FtsZ, SepF, SepF2, and the FtsZ-positioning protein SsgB.
|
|
